diff --git "a/parrot/lib/python3.10/site-packages/scipy/stats/_multivariate.py" "b/parrot/lib/python3.10/site-packages/scipy/stats/_multivariate.py" new file mode 100644--- /dev/null +++ "b/parrot/lib/python3.10/site-packages/scipy/stats/_multivariate.py" @@ -0,0 +1,6981 @@ +# +# Author: Joris Vankerschaver 2013 +# +import math +import numpy as np +import scipy.linalg +from scipy._lib import doccer +from scipy.special import (gammaln, psi, multigammaln, xlogy, entr, betaln, + ive, loggamma) +from scipy._lib._util import check_random_state, _lazywhere +from scipy.linalg.blas import drot, get_blas_funcs +from ._continuous_distns import norm +from ._discrete_distns import binom +from . import _mvn, _covariance, _rcont +from ._qmvnt import _qmvt +from ._morestats import directional_stats +from scipy.optimize import root_scalar + +__all__ = ['multivariate_normal', + 'matrix_normal', + 'dirichlet', + 'dirichlet_multinomial', + 'wishart', + 'invwishart', + 'multinomial', + 'special_ortho_group', + 'ortho_group', + 'random_correlation', + 'unitary_group', + 'multivariate_t', + 'multivariate_hypergeom', + 'random_table', + 'uniform_direction', + 'vonmises_fisher'] + +_LOG_2PI = np.log(2 * np.pi) +_LOG_2 = np.log(2) +_LOG_PI = np.log(np.pi) + + +_doc_random_state = """\ +seed : {None, int, np.random.RandomState, np.random.Generator}, optional + Used for drawing random variates. + If `seed` is `None`, the `~np.random.RandomState` singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, seeded + with seed. + If `seed` is already a ``RandomState`` or ``Generator`` instance, + then that object is used. + Default is `None`. +""" + + +def _squeeze_output(out): + """ + Remove single-dimensional entries from array and convert to scalar, + if necessary. + """ + out = out.squeeze() + if out.ndim == 0: + out = out[()] + return out + + +def _eigvalsh_to_eps(spectrum, cond=None, rcond=None): + """Determine which eigenvalues are "small" given the spectrum. + + This is for compatibility across various linear algebra functions + that should agree about whether or not a Hermitian matrix is numerically + singular and what is its numerical matrix rank. + This is designed to be compatible with scipy.linalg.pinvh. + + Parameters + ---------- + spectrum : 1d ndarray + Array of eigenvalues of a Hermitian matrix. + cond, rcond : float, optional + Cutoff for small eigenvalues. + Singular values smaller than rcond * largest_eigenvalue are + considered zero. + If None or -1, suitable machine precision is used. + + Returns + ------- + eps : float + Magnitude cutoff for numerical negligibility. + + """ + if rcond is not None: + cond = rcond + if cond in [None, -1]: + t = spectrum.dtype.char.lower() + factor = {'f': 1E3, 'd': 1E6} + cond = factor[t] * np.finfo(t).eps + eps = cond * np.max(abs(spectrum)) + return eps + + +def _pinv_1d(v, eps=1e-5): + """A helper function for computing the pseudoinverse. + + Parameters + ---------- + v : iterable of numbers + This may be thought of as a vector of eigenvalues or singular values. + eps : float + Values with magnitude no greater than eps are considered negligible. + + Returns + ------- + v_pinv : 1d float ndarray + A vector of pseudo-inverted numbers. + + """ + return np.array([0 if abs(x) <= eps else 1/x for x in v], dtype=float) + + +class _PSD: + """ + Compute coordinated functions of a symmetric positive semidefinite matrix. + + This class addresses two issues. Firstly it allows the pseudoinverse, + the logarithm of the pseudo-determinant, and the rank of the matrix + to be computed using one call to eigh instead of three. + Secondly it allows these functions to be computed in a way + that gives mutually compatible results. + All of the functions are computed with a common understanding as to + which of the eigenvalues are to be considered negligibly small. + The functions are designed to coordinate with scipy.linalg.pinvh() + but not necessarily with np.linalg.det() or with np.linalg.matrix_rank(). + + Parameters + ---------- + M : array_like + Symmetric positive semidefinite matrix (2-D). + cond, rcond : float, optional + Cutoff for small eigenvalues. + Singular values smaller than rcond * largest_eigenvalue are + considered zero. + If None or -1, suitable machine precision is used. + lower : bool, optional + Whether the pertinent array data is taken from the lower + or upper triangle of M. (Default: lower) + check_finite : bool, optional + Whether to check that the input matrices contain only finite + numbers. Disabling may give a performance gain, but may result + in problems (crashes, non-termination) if the inputs do contain + infinities or NaNs. + allow_singular : bool, optional + Whether to allow a singular matrix. (Default: True) + + Notes + ----- + The arguments are similar to those of scipy.linalg.pinvh(). + + """ + + def __init__(self, M, cond=None, rcond=None, lower=True, + check_finite=True, allow_singular=True): + self._M = np.asarray(M) + + # Compute the symmetric eigendecomposition. + # Note that eigh takes care of array conversion, chkfinite, + # and assertion that the matrix is square. + s, u = scipy.linalg.eigh(M, lower=lower, check_finite=check_finite) + + eps = _eigvalsh_to_eps(s, cond, rcond) + if np.min(s) < -eps: + msg = "The input matrix must be symmetric positive semidefinite." + raise ValueError(msg) + d = s[s > eps] + if len(d) < len(s) and not allow_singular: + msg = ("When `allow_singular is False`, the input matrix must be " + "symmetric positive definite.") + raise np.linalg.LinAlgError(msg) + s_pinv = _pinv_1d(s, eps) + U = np.multiply(u, np.sqrt(s_pinv)) + + # Save the eigenvector basis, and tolerance for testing support + self.eps = 1e3*eps + self.V = u[:, s <= eps] + + # Initialize the eagerly precomputed attributes. + self.rank = len(d) + self.U = U + self.log_pdet = np.sum(np.log(d)) + + # Initialize attributes to be lazily computed. + self._pinv = None + + def _support_mask(self, x): + """ + Check whether x lies in the support of the distribution. + """ + residual = np.linalg.norm(x @ self.V, axis=-1) + in_support = residual < self.eps + return in_support + + @property + def pinv(self): + if self._pinv is None: + self._pinv = np.dot(self.U, self.U.T) + return self._pinv + + +class multi_rv_generic: + """ + Class which encapsulates common functionality between all multivariate + distributions. + """ + def __init__(self, seed=None): + super().__init__() + self._random_state = check_random_state(seed) + + @property + def random_state(self): + """ Get or set the Generator object for generating random variates. + + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance then + that instance is used. + + """ + return self._random_state + + @random_state.setter + def random_state(self, seed): + self._random_state = check_random_state(seed) + + def _get_random_state(self, random_state): + if random_state is not None: + return check_random_state(random_state) + else: + return self._random_state + + +class multi_rv_frozen: + """ + Class which encapsulates common functionality between all frozen + multivariate distributions. + """ + @property + def random_state(self): + return self._dist._random_state + + @random_state.setter + def random_state(self, seed): + self._dist._random_state = check_random_state(seed) + + +_mvn_doc_default_callparams = """\ +mean : array_like, default: ``[0]`` + Mean of the distribution. +cov : array_like or `Covariance`, default: ``[1]`` + Symmetric positive (semi)definite covariance matrix of the distribution. +allow_singular : bool, default: ``False`` + Whether to allow a singular covariance matrix. This is ignored if `cov` is + a `Covariance` object. +""" + +_mvn_doc_callparams_note = """\ +Setting the parameter `mean` to `None` is equivalent to having `mean` +be the zero-vector. The parameter `cov` can be a scalar, in which case +the covariance matrix is the identity times that value, a vector of +diagonal entries for the covariance matrix, a two-dimensional array_like, +or a `Covariance` object. +""" + +_mvn_doc_frozen_callparams = "" + +_mvn_doc_frozen_callparams_note = """\ +See class definition for a detailed description of parameters.""" + +mvn_docdict_params = { + '_mvn_doc_default_callparams': _mvn_doc_default_callparams, + '_mvn_doc_callparams_note': _mvn_doc_callparams_note, + '_doc_random_state': _doc_random_state +} + +mvn_docdict_noparams = { + '_mvn_doc_default_callparams': _mvn_doc_frozen_callparams, + '_mvn_doc_callparams_note': _mvn_doc_frozen_callparams_note, + '_doc_random_state': _doc_random_state +} + + +class multivariate_normal_gen(multi_rv_generic): + r"""A multivariate normal random variable. + + The `mean` keyword specifies the mean. The `cov` keyword specifies the + covariance matrix. + + Methods + ------- + pdf(x, mean=None, cov=1, allow_singular=False) + Probability density function. + logpdf(x, mean=None, cov=1, allow_singular=False) + Log of the probability density function. + cdf(x, mean=None, cov=1, allow_singular=False, maxpts=1000000*dim, abseps=1e-5, releps=1e-5, lower_limit=None) + Cumulative distribution function. + logcdf(x, mean=None, cov=1, allow_singular=False, maxpts=1000000*dim, abseps=1e-5, releps=1e-5) + Log of the cumulative distribution function. + rvs(mean=None, cov=1, size=1, random_state=None) + Draw random samples from a multivariate normal distribution. + entropy(mean=None, cov=1) + Compute the differential entropy of the multivariate normal. + fit(x, fix_mean=None, fix_cov=None) + Fit a multivariate normal distribution to data. + + Parameters + ---------- + %(_mvn_doc_default_callparams)s + %(_doc_random_state)s + + Notes + ----- + %(_mvn_doc_callparams_note)s + + The covariance matrix `cov` may be an instance of a subclass of + `Covariance`, e.g. `scipy.stats.CovViaPrecision`. If so, `allow_singular` + is ignored. + + Otherwise, `cov` must be a symmetric positive semidefinite + matrix when `allow_singular` is True; it must be (strictly) positive + definite when `allow_singular` is False. + Symmetry is not checked; only the lower triangular portion is used. + The determinant and inverse of `cov` are computed + as the pseudo-determinant and pseudo-inverse, respectively, so + that `cov` does not need to have full rank. + + The probability density function for `multivariate_normal` is + + .. math:: + + f(x) = \frac{1}{\sqrt{(2 \pi)^k \det \Sigma}} + \exp\left( -\frac{1}{2} (x - \mu)^T \Sigma^{-1} (x - \mu) \right), + + where :math:`\mu` is the mean, :math:`\Sigma` the covariance matrix, + :math:`k` the rank of :math:`\Sigma`. In case of singular :math:`\Sigma`, + SciPy extends this definition according to [1]_. + + .. versionadded:: 0.14.0 + + References + ---------- + .. [1] Multivariate Normal Distribution - Degenerate Case, Wikipedia, + https://en.wikipedia.org/wiki/Multivariate_normal_distribution#Degenerate_case + + Examples + -------- + >>> import numpy as np + >>> import matplotlib.pyplot as plt + >>> from scipy.stats import multivariate_normal + + >>> x = np.linspace(0, 5, 10, endpoint=False) + >>> y = multivariate_normal.pdf(x, mean=2.5, cov=0.5); y + array([ 0.00108914, 0.01033349, 0.05946514, 0.20755375, 0.43939129, + 0.56418958, 0.43939129, 0.20755375, 0.05946514, 0.01033349]) + >>> fig1 = plt.figure() + >>> ax = fig1.add_subplot(111) + >>> ax.plot(x, y) + >>> plt.show() + + Alternatively, the object may be called (as a function) to fix the mean + and covariance parameters, returning a "frozen" multivariate normal + random variable: + + >>> rv = multivariate_normal(mean=None, cov=1, allow_singular=False) + >>> # Frozen object with the same methods but holding the given + >>> # mean and covariance fixed. + + The input quantiles can be any shape of array, as long as the last + axis labels the components. This allows us for instance to + display the frozen pdf for a non-isotropic random variable in 2D as + follows: + + >>> x, y = np.mgrid[-1:1:.01, -1:1:.01] + >>> pos = np.dstack((x, y)) + >>> rv = multivariate_normal([0.5, -0.2], [[2.0, 0.3], [0.3, 0.5]]) + >>> fig2 = plt.figure() + >>> ax2 = fig2.add_subplot(111) + >>> ax2.contourf(x, y, rv.pdf(pos)) + + """ # noqa: E501 + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__, mvn_docdict_params) + + def __call__(self, mean=None, cov=1, allow_singular=False, seed=None): + """Create a frozen multivariate normal distribution. + + See `multivariate_normal_frozen` for more information. + """ + return multivariate_normal_frozen(mean, cov, + allow_singular=allow_singular, + seed=seed) + + def _process_parameters(self, mean, cov, allow_singular=True): + """ + Infer dimensionality from mean or covariance matrix, ensure that + mean and covariance are full vector resp. matrix. + """ + if isinstance(cov, _covariance.Covariance): + return self._process_parameters_Covariance(mean, cov) + else: + # Before `Covariance` classes were introduced, + # `multivariate_normal` accepted plain arrays as `cov` and used the + # following input validation. To avoid disturbing the behavior of + # `multivariate_normal` when plain arrays are used, we use the + # original input validation here. + dim, mean, cov = self._process_parameters_psd(None, mean, cov) + # After input validation, some methods then processed the arrays + # with a `_PSD` object and used that to perform computation. + # To avoid branching statements in each method depending on whether + # `cov` is an array or `Covariance` object, we always process the + # array with `_PSD`, and then use wrapper that satisfies the + # `Covariance` interface, `CovViaPSD`. + psd = _PSD(cov, allow_singular=allow_singular) + cov_object = _covariance.CovViaPSD(psd) + return dim, mean, cov_object + + def _process_parameters_Covariance(self, mean, cov): + dim = cov.shape[-1] + mean = np.array([0.]) if mean is None else mean + message = (f"`cov` represents a covariance matrix in {dim} dimensions," + f"and so `mean` must be broadcastable to shape {(dim,)}") + try: + mean = np.broadcast_to(mean, dim) + except ValueError as e: + raise ValueError(message) from e + return dim, mean, cov + + def _process_parameters_psd(self, dim, mean, cov): + # Try to infer dimensionality + if dim is None: + if mean is None: + if cov is None: + dim = 1 + else: + cov = np.asarray(cov, dtype=float) + if cov.ndim < 2: + dim = 1 + else: + dim = cov.shape[0] + else: + mean = np.asarray(mean, dtype=float) + dim = mean.size + else: + if not np.isscalar(dim): + raise ValueError("Dimension of random variable must be " + "a scalar.") + + # Check input sizes and return full arrays for mean and cov if + # necessary + if mean is None: + mean = np.zeros(dim) + mean = np.asarray(mean, dtype=float) + + if cov is None: + cov = 1.0 + cov = np.asarray(cov, dtype=float) + + if dim == 1: + mean = mean.reshape(1) + cov = cov.reshape(1, 1) + + if mean.ndim != 1 or mean.shape[0] != dim: + raise ValueError("Array 'mean' must be a vector of length %d." % + dim) + if cov.ndim == 0: + cov = cov * np.eye(dim) + elif cov.ndim == 1: + cov = np.diag(cov) + elif cov.ndim == 2 and cov.shape != (dim, dim): + rows, cols = cov.shape + if rows != cols: + msg = ("Array 'cov' must be square if it is two dimensional," + " but cov.shape = %s." % str(cov.shape)) + else: + msg = ("Dimension mismatch: array 'cov' is of shape %s," + " but 'mean' is a vector of length %d.") + msg = msg % (str(cov.shape), len(mean)) + raise ValueError(msg) + elif cov.ndim > 2: + raise ValueError("Array 'cov' must be at most two-dimensional," + " but cov.ndim = %d" % cov.ndim) + + return dim, mean, cov + + def _process_quantiles(self, x, dim): + """ + Adjust quantiles array so that last axis labels the components of + each data point. + """ + x = np.asarray(x, dtype=float) + + if x.ndim == 0: + x = x[np.newaxis] + elif x.ndim == 1: + if dim == 1: + x = x[:, np.newaxis] + else: + x = x[np.newaxis, :] + + return x + + def _logpdf(self, x, mean, cov_object): + """Log of the multivariate normal probability density function. + + Parameters + ---------- + x : ndarray + Points at which to evaluate the log of the probability + density function + mean : ndarray + Mean of the distribution + cov_object : Covariance + An object representing the Covariance matrix + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'logpdf' instead. + + """ + log_det_cov, rank = cov_object.log_pdet, cov_object.rank + dev = x - mean + if dev.ndim > 1: + log_det_cov = log_det_cov[..., np.newaxis] + rank = rank[..., np.newaxis] + maha = np.sum(np.square(cov_object.whiten(dev)), axis=-1) + return -0.5 * (rank * _LOG_2PI + log_det_cov + maha) + + def logpdf(self, x, mean=None, cov=1, allow_singular=False): + """Log of the multivariate normal probability density function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + %(_mvn_doc_default_callparams)s + + Returns + ------- + pdf : ndarray or scalar + Log of the probability density function evaluated at `x` + + Notes + ----- + %(_mvn_doc_callparams_note)s + + """ + params = self._process_parameters(mean, cov, allow_singular) + dim, mean, cov_object = params + x = self._process_quantiles(x, dim) + out = self._logpdf(x, mean, cov_object) + if np.any(cov_object.rank < dim): + out_of_bounds = ~cov_object._support_mask(x-mean) + out[out_of_bounds] = -np.inf + return _squeeze_output(out) + + def pdf(self, x, mean=None, cov=1, allow_singular=False): + """Multivariate normal probability density function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + %(_mvn_doc_default_callparams)s + + Returns + ------- + pdf : ndarray or scalar + Probability density function evaluated at `x` + + Notes + ----- + %(_mvn_doc_callparams_note)s + + """ + params = self._process_parameters(mean, cov, allow_singular) + dim, mean, cov_object = params + x = self._process_quantiles(x, dim) + out = np.exp(self._logpdf(x, mean, cov_object)) + if np.any(cov_object.rank < dim): + out_of_bounds = ~cov_object._support_mask(x-mean) + out[out_of_bounds] = 0.0 + return _squeeze_output(out) + + def _cdf(self, x, mean, cov, maxpts, abseps, releps, lower_limit): + """Multivariate normal cumulative distribution function. + + Parameters + ---------- + x : ndarray + Points at which to evaluate the cumulative distribution function. + mean : ndarray + Mean of the distribution + cov : array_like + Covariance matrix of the distribution + maxpts : integer + The maximum number of points to use for integration + abseps : float + Absolute error tolerance + releps : float + Relative error tolerance + lower_limit : array_like, optional + Lower limit of integration of the cumulative distribution function. + Default is negative infinity. Must be broadcastable with `x`. + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'cdf' instead. + + + .. versionadded:: 1.0.0 + + """ + lower = (np.full(mean.shape, -np.inf) + if lower_limit is None else lower_limit) + # In 2d, _mvn.mvnun accepts input in which `lower` bound elements + # are greater than `x`. Not so in other dimensions. Fix this by + # ensuring that lower bounds are indeed lower when passed, then + # set signs of resulting CDF manually. + b, a = np.broadcast_arrays(x, lower) + i_swap = b < a + signs = (-1)**(i_swap.sum(axis=-1)) # odd # of swaps -> negative + a, b = a.copy(), b.copy() + a[i_swap], b[i_swap] = b[i_swap], a[i_swap] + n = x.shape[-1] + limits = np.concatenate((a, b), axis=-1) + + # mvnun expects 1-d arguments, so process points sequentially + def func1d(limits): + return _mvn.mvnun(limits[:n], limits[n:], mean, cov, + maxpts, abseps, releps)[0] + + out = np.apply_along_axis(func1d, -1, limits) * signs + return _squeeze_output(out) + + def logcdf(self, x, mean=None, cov=1, allow_singular=False, maxpts=None, + abseps=1e-5, releps=1e-5, *, lower_limit=None): + """Log of the multivariate normal cumulative distribution function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + %(_mvn_doc_default_callparams)s + maxpts : integer, optional + The maximum number of points to use for integration + (default `1000000*dim`) + abseps : float, optional + Absolute error tolerance (default 1e-5) + releps : float, optional + Relative error tolerance (default 1e-5) + lower_limit : array_like, optional + Lower limit of integration of the cumulative distribution function. + Default is negative infinity. Must be broadcastable with `x`. + + Returns + ------- + cdf : ndarray or scalar + Log of the cumulative distribution function evaluated at `x` + + Notes + ----- + %(_mvn_doc_callparams_note)s + + .. versionadded:: 1.0.0 + + """ + params = self._process_parameters(mean, cov, allow_singular) + dim, mean, cov_object = params + cov = cov_object.covariance + x = self._process_quantiles(x, dim) + if not maxpts: + maxpts = 1000000 * dim + cdf = self._cdf(x, mean, cov, maxpts, abseps, releps, lower_limit) + # the log of a negative real is complex, and cdf can be negative + # if lower limit is greater than upper limit + cdf = cdf + 0j if np.any(cdf < 0) else cdf + out = np.log(cdf) + return out + + def cdf(self, x, mean=None, cov=1, allow_singular=False, maxpts=None, + abseps=1e-5, releps=1e-5, *, lower_limit=None): + """Multivariate normal cumulative distribution function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + %(_mvn_doc_default_callparams)s + maxpts : integer, optional + The maximum number of points to use for integration + (default `1000000*dim`) + abseps : float, optional + Absolute error tolerance (default 1e-5) + releps : float, optional + Relative error tolerance (default 1e-5) + lower_limit : array_like, optional + Lower limit of integration of the cumulative distribution function. + Default is negative infinity. Must be broadcastable with `x`. + + Returns + ------- + cdf : ndarray or scalar + Cumulative distribution function evaluated at `x` + + Notes + ----- + %(_mvn_doc_callparams_note)s + + .. versionadded:: 1.0.0 + + """ + params = self._process_parameters(mean, cov, allow_singular) + dim, mean, cov_object = params + cov = cov_object.covariance + x = self._process_quantiles(x, dim) + if not maxpts: + maxpts = 1000000 * dim + out = self._cdf(x, mean, cov, maxpts, abseps, releps, lower_limit) + return out + + def rvs(self, mean=None, cov=1, size=1, random_state=None): + """Draw random samples from a multivariate normal distribution. + + Parameters + ---------- + %(_mvn_doc_default_callparams)s + size : integer, optional + Number of samples to draw (default 1). + %(_doc_random_state)s + + Returns + ------- + rvs : ndarray or scalar + Random variates of size (`size`, `N`), where `N` is the + dimension of the random variable. + + Notes + ----- + %(_mvn_doc_callparams_note)s + + """ + dim, mean, cov_object = self._process_parameters(mean, cov) + random_state = self._get_random_state(random_state) + + if isinstance(cov_object, _covariance.CovViaPSD): + cov = cov_object.covariance + out = random_state.multivariate_normal(mean, cov, size) + out = _squeeze_output(out) + else: + size = size or tuple() + if not np.iterable(size): + size = (size,) + shape = tuple(size) + (cov_object.shape[-1],) + x = random_state.normal(size=shape) + out = mean + cov_object.colorize(x) + return out + + def entropy(self, mean=None, cov=1): + """Compute the differential entropy of the multivariate normal. + + Parameters + ---------- + %(_mvn_doc_default_callparams)s + + Returns + ------- + h : scalar + Entropy of the multivariate normal distribution + + Notes + ----- + %(_mvn_doc_callparams_note)s + + """ + dim, mean, cov_object = self._process_parameters(mean, cov) + return 0.5 * (cov_object.rank * (_LOG_2PI + 1) + cov_object.log_pdet) + + def fit(self, x, fix_mean=None, fix_cov=None): + """Fit a multivariate normal distribution to data. + + Parameters + ---------- + x : ndarray (m, n) + Data the distribution is fitted to. Must have two axes. + The first axis of length `m` represents the number of vectors + the distribution is fitted to. The second axis of length `n` + determines the dimensionality of the fitted distribution. + fix_mean : ndarray(n, ) + Fixed mean vector. Must have length `n`. + fix_cov: ndarray (n, n) + Fixed covariance matrix. Must have shape `(n, n)`. + + Returns + ------- + mean : ndarray (n, ) + Maximum likelihood estimate of the mean vector + cov : ndarray (n, n) + Maximum likelihood estimate of the covariance matrix + + """ + # input validation for data to be fitted + x = np.asarray(x) + if x.ndim != 2: + raise ValueError("`x` must be two-dimensional.") + + n_vectors, dim = x.shape + + # parameter estimation + # reference: https://home.ttic.edu/~shubhendu/Slides/Estimation.pdf + if fix_mean is not None: + # input validation for `fix_mean` + fix_mean = np.atleast_1d(fix_mean) + if fix_mean.shape != (dim, ): + msg = ("`fix_mean` must be a one-dimensional array the same " + "length as the dimensionality of the vectors `x`.") + raise ValueError(msg) + mean = fix_mean + else: + mean = x.mean(axis=0) + + if fix_cov is not None: + # input validation for `fix_cov` + fix_cov = np.atleast_2d(fix_cov) + # validate shape + if fix_cov.shape != (dim, dim): + msg = ("`fix_cov` must be a two-dimensional square array " + "of same side length as the dimensionality of the " + "vectors `x`.") + raise ValueError(msg) + # validate positive semidefiniteness + # a trimmed down copy from _PSD + s, u = scipy.linalg.eigh(fix_cov, lower=True, check_finite=True) + eps = _eigvalsh_to_eps(s) + if np.min(s) < -eps: + msg = "`fix_cov` must be symmetric positive semidefinite." + raise ValueError(msg) + cov = fix_cov + else: + centered_data = x - mean + cov = centered_data.T @ centered_data / n_vectors + return mean, cov + + +multivariate_normal = multivariate_normal_gen() + + +class multivariate_normal_frozen(multi_rv_frozen): + def __init__(self, mean=None, cov=1, allow_singular=False, seed=None, + maxpts=None, abseps=1e-5, releps=1e-5): + """Create a frozen multivariate normal distribution. + + Parameters + ---------- + mean : array_like, default: ``[0]`` + Mean of the distribution. + cov : array_like, default: ``[1]`` + Symmetric positive (semi)definite covariance matrix of the + distribution. + allow_singular : bool, default: ``False`` + Whether to allow a singular covariance matrix. + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + maxpts : integer, optional + The maximum number of points to use for integration of the + cumulative distribution function (default `1000000*dim`) + abseps : float, optional + Absolute error tolerance for the cumulative distribution function + (default 1e-5) + releps : float, optional + Relative error tolerance for the cumulative distribution function + (default 1e-5) + + Examples + -------- + When called with the default parameters, this will create a 1D random + variable with mean 0 and covariance 1: + + >>> from scipy.stats import multivariate_normal + >>> r = multivariate_normal() + >>> r.mean + array([ 0.]) + >>> r.cov + array([[1.]]) + + """ # numpy/numpydoc#87 # noqa: E501 + self._dist = multivariate_normal_gen(seed) + self.dim, self.mean, self.cov_object = ( + self._dist._process_parameters(mean, cov, allow_singular)) + self.allow_singular = allow_singular or self.cov_object._allow_singular + if not maxpts: + maxpts = 1000000 * self.dim + self.maxpts = maxpts + self.abseps = abseps + self.releps = releps + + @property + def cov(self): + return self.cov_object.covariance + + def logpdf(self, x): + x = self._dist._process_quantiles(x, self.dim) + out = self._dist._logpdf(x, self.mean, self.cov_object) + if np.any(self.cov_object.rank < self.dim): + out_of_bounds = ~self.cov_object._support_mask(x-self.mean) + out[out_of_bounds] = -np.inf + return _squeeze_output(out) + + def pdf(self, x): + return np.exp(self.logpdf(x)) + + def logcdf(self, x, *, lower_limit=None): + cdf = self.cdf(x, lower_limit=lower_limit) + # the log of a negative real is complex, and cdf can be negative + # if lower limit is greater than upper limit + cdf = cdf + 0j if np.any(cdf < 0) else cdf + out = np.log(cdf) + return out + + def cdf(self, x, *, lower_limit=None): + x = self._dist._process_quantiles(x, self.dim) + out = self._dist._cdf(x, self.mean, self.cov_object.covariance, + self.maxpts, self.abseps, self.releps, + lower_limit) + return _squeeze_output(out) + + def rvs(self, size=1, random_state=None): + return self._dist.rvs(self.mean, self.cov_object, size, random_state) + + def entropy(self): + """Computes the differential entropy of the multivariate normal. + + Returns + ------- + h : scalar + Entropy of the multivariate normal distribution + + """ + log_pdet = self.cov_object.log_pdet + rank = self.cov_object.rank + return 0.5 * (rank * (_LOG_2PI + 1) + log_pdet) + + +# Set frozen generator docstrings from corresponding docstrings in +# multivariate_normal_gen and fill in default strings in class docstrings +for name in ['logpdf', 'pdf', 'logcdf', 'cdf', 'rvs']: + method = multivariate_normal_gen.__dict__[name] + method_frozen = multivariate_normal_frozen.__dict__[name] + method_frozen.__doc__ = doccer.docformat(method.__doc__, + mvn_docdict_noparams) + method.__doc__ = doccer.docformat(method.__doc__, mvn_docdict_params) + +_matnorm_doc_default_callparams = """\ +mean : array_like, optional + Mean of the distribution (default: `None`) +rowcov : array_like, optional + Among-row covariance matrix of the distribution (default: `1`) +colcov : array_like, optional + Among-column covariance matrix of the distribution (default: `1`) +""" + +_matnorm_doc_callparams_note = """\ +If `mean` is set to `None` then a matrix of zeros is used for the mean. +The dimensions of this matrix are inferred from the shape of `rowcov` and +`colcov`, if these are provided, or set to `1` if ambiguous. + +`rowcov` and `colcov` can be two-dimensional array_likes specifying the +covariance matrices directly. Alternatively, a one-dimensional array will +be be interpreted as the entries of a diagonal matrix, and a scalar or +zero-dimensional array will be interpreted as this value times the +identity matrix. +""" + +_matnorm_doc_frozen_callparams = "" + +_matnorm_doc_frozen_callparams_note = """\ +See class definition for a detailed description of parameters.""" + +matnorm_docdict_params = { + '_matnorm_doc_default_callparams': _matnorm_doc_default_callparams, + '_matnorm_doc_callparams_note': _matnorm_doc_callparams_note, + '_doc_random_state': _doc_random_state +} + +matnorm_docdict_noparams = { + '_matnorm_doc_default_callparams': _matnorm_doc_frozen_callparams, + '_matnorm_doc_callparams_note': _matnorm_doc_frozen_callparams_note, + '_doc_random_state': _doc_random_state +} + + +class matrix_normal_gen(multi_rv_generic): + r"""A matrix normal random variable. + + The `mean` keyword specifies the mean. The `rowcov` keyword specifies the + among-row covariance matrix. The 'colcov' keyword specifies the + among-column covariance matrix. + + Methods + ------- + pdf(X, mean=None, rowcov=1, colcov=1) + Probability density function. + logpdf(X, mean=None, rowcov=1, colcov=1) + Log of the probability density function. + rvs(mean=None, rowcov=1, colcov=1, size=1, random_state=None) + Draw random samples. + entropy(rowcol=1, colcov=1) + Differential entropy. + + Parameters + ---------- + %(_matnorm_doc_default_callparams)s + %(_doc_random_state)s + + Notes + ----- + %(_matnorm_doc_callparams_note)s + + The covariance matrices specified by `rowcov` and `colcov` must be + (symmetric) positive definite. If the samples in `X` are + :math:`m \times n`, then `rowcov` must be :math:`m \times m` and + `colcov` must be :math:`n \times n`. `mean` must be the same shape as `X`. + + The probability density function for `matrix_normal` is + + .. math:: + + f(X) = (2 \pi)^{-\frac{mn}{2}}|U|^{-\frac{n}{2}} |V|^{-\frac{m}{2}} + \exp\left( -\frac{1}{2} \mathrm{Tr}\left[ U^{-1} (X-M) V^{-1} + (X-M)^T \right] \right), + + where :math:`M` is the mean, :math:`U` the among-row covariance matrix, + :math:`V` the among-column covariance matrix. + + The `allow_singular` behaviour of the `multivariate_normal` + distribution is not currently supported. Covariance matrices must be + full rank. + + The `matrix_normal` distribution is closely related to the + `multivariate_normal` distribution. Specifically, :math:`\mathrm{Vec}(X)` + (the vector formed by concatenating the columns of :math:`X`) has a + multivariate normal distribution with mean :math:`\mathrm{Vec}(M)` + and covariance :math:`V \otimes U` (where :math:`\otimes` is the Kronecker + product). Sampling and pdf evaluation are + :math:`\mathcal{O}(m^3 + n^3 + m^2 n + m n^2)` for the matrix normal, but + :math:`\mathcal{O}(m^3 n^3)` for the equivalent multivariate normal, + making this equivalent form algorithmically inefficient. + + .. versionadded:: 0.17.0 + + Examples + -------- + + >>> import numpy as np + >>> from scipy.stats import matrix_normal + + >>> M = np.arange(6).reshape(3,2); M + array([[0, 1], + [2, 3], + [4, 5]]) + >>> U = np.diag([1,2,3]); U + array([[1, 0, 0], + [0, 2, 0], + [0, 0, 3]]) + >>> V = 0.3*np.identity(2); V + array([[ 0.3, 0. ], + [ 0. , 0.3]]) + >>> X = M + 0.1; X + array([[ 0.1, 1.1], + [ 2.1, 3.1], + [ 4.1, 5.1]]) + >>> matrix_normal.pdf(X, mean=M, rowcov=U, colcov=V) + 0.023410202050005054 + + >>> # Equivalent multivariate normal + >>> from scipy.stats import multivariate_normal + >>> vectorised_X = X.T.flatten() + >>> equiv_mean = M.T.flatten() + >>> equiv_cov = np.kron(V,U) + >>> multivariate_normal.pdf(vectorised_X, mean=equiv_mean, cov=equiv_cov) + 0.023410202050005054 + + Alternatively, the object may be called (as a function) to fix the mean + and covariance parameters, returning a "frozen" matrix normal + random variable: + + >>> rv = matrix_normal(mean=None, rowcov=1, colcov=1) + >>> # Frozen object with the same methods but holding the given + >>> # mean and covariance fixed. + + """ + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__, matnorm_docdict_params) + + def __call__(self, mean=None, rowcov=1, colcov=1, seed=None): + """Create a frozen matrix normal distribution. + + See `matrix_normal_frozen` for more information. + + """ + return matrix_normal_frozen(mean, rowcov, colcov, seed=seed) + + def _process_parameters(self, mean, rowcov, colcov): + """ + Infer dimensionality from mean or covariance matrices. Handle + defaults. Ensure compatible dimensions. + """ + + # Process mean + if mean is not None: + mean = np.asarray(mean, dtype=float) + meanshape = mean.shape + if len(meanshape) != 2: + raise ValueError("Array `mean` must be two dimensional.") + if np.any(meanshape == 0): + raise ValueError("Array `mean` has invalid shape.") + + # Process among-row covariance + rowcov = np.asarray(rowcov, dtype=float) + if rowcov.ndim == 0: + if mean is not None: + rowcov = rowcov * np.identity(meanshape[0]) + else: + rowcov = rowcov * np.identity(1) + elif rowcov.ndim == 1: + rowcov = np.diag(rowcov) + rowshape = rowcov.shape + if len(rowshape) != 2: + raise ValueError("`rowcov` must be a scalar or a 2D array.") + if rowshape[0] != rowshape[1]: + raise ValueError("Array `rowcov` must be square.") + if rowshape[0] == 0: + raise ValueError("Array `rowcov` has invalid shape.") + numrows = rowshape[0] + + # Process among-column covariance + colcov = np.asarray(colcov, dtype=float) + if colcov.ndim == 0: + if mean is not None: + colcov = colcov * np.identity(meanshape[1]) + else: + colcov = colcov * np.identity(1) + elif colcov.ndim == 1: + colcov = np.diag(colcov) + colshape = colcov.shape + if len(colshape) != 2: + raise ValueError("`colcov` must be a scalar or a 2D array.") + if colshape[0] != colshape[1]: + raise ValueError("Array `colcov` must be square.") + if colshape[0] == 0: + raise ValueError("Array `colcov` has invalid shape.") + numcols = colshape[0] + + # Ensure mean and covariances compatible + if mean is not None: + if meanshape[0] != numrows: + raise ValueError("Arrays `mean` and `rowcov` must have the " + "same number of rows.") + if meanshape[1] != numcols: + raise ValueError("Arrays `mean` and `colcov` must have the " + "same number of columns.") + else: + mean = np.zeros((numrows, numcols)) + + dims = (numrows, numcols) + + return dims, mean, rowcov, colcov + + def _process_quantiles(self, X, dims): + """ + Adjust quantiles array so that last two axes labels the components of + each data point. + """ + X = np.asarray(X, dtype=float) + if X.ndim == 2: + X = X[np.newaxis, :] + if X.shape[-2:] != dims: + raise ValueError("The shape of array `X` is not compatible " + "with the distribution parameters.") + return X + + def _logpdf(self, dims, X, mean, row_prec_rt, log_det_rowcov, + col_prec_rt, log_det_colcov): + """Log of the matrix normal probability density function. + + Parameters + ---------- + dims : tuple + Dimensions of the matrix variates + X : ndarray + Points at which to evaluate the log of the probability + density function + mean : ndarray + Mean of the distribution + row_prec_rt : ndarray + A decomposition such that np.dot(row_prec_rt, row_prec_rt.T) + is the inverse of the among-row covariance matrix + log_det_rowcov : float + Logarithm of the determinant of the among-row covariance matrix + col_prec_rt : ndarray + A decomposition such that np.dot(col_prec_rt, col_prec_rt.T) + is the inverse of the among-column covariance matrix + log_det_colcov : float + Logarithm of the determinant of the among-column covariance matrix + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'logpdf' instead. + + """ + numrows, numcols = dims + roll_dev = np.moveaxis(X-mean, -1, 0) + scale_dev = np.tensordot(col_prec_rt.T, + np.dot(roll_dev, row_prec_rt), 1) + maha = np.sum(np.sum(np.square(scale_dev), axis=-1), axis=0) + return -0.5 * (numrows*numcols*_LOG_2PI + numcols*log_det_rowcov + + numrows*log_det_colcov + maha) + + def logpdf(self, X, mean=None, rowcov=1, colcov=1): + """Log of the matrix normal probability density function. + + Parameters + ---------- + X : array_like + Quantiles, with the last two axes of `X` denoting the components. + %(_matnorm_doc_default_callparams)s + + Returns + ------- + logpdf : ndarray + Log of the probability density function evaluated at `X` + + Notes + ----- + %(_matnorm_doc_callparams_note)s + + """ + dims, mean, rowcov, colcov = self._process_parameters(mean, rowcov, + colcov) + X = self._process_quantiles(X, dims) + rowpsd = _PSD(rowcov, allow_singular=False) + colpsd = _PSD(colcov, allow_singular=False) + out = self._logpdf(dims, X, mean, rowpsd.U, rowpsd.log_pdet, colpsd.U, + colpsd.log_pdet) + return _squeeze_output(out) + + def pdf(self, X, mean=None, rowcov=1, colcov=1): + """Matrix normal probability density function. + + Parameters + ---------- + X : array_like + Quantiles, with the last two axes of `X` denoting the components. + %(_matnorm_doc_default_callparams)s + + Returns + ------- + pdf : ndarray + Probability density function evaluated at `X` + + Notes + ----- + %(_matnorm_doc_callparams_note)s + + """ + return np.exp(self.logpdf(X, mean, rowcov, colcov)) + + def rvs(self, mean=None, rowcov=1, colcov=1, size=1, random_state=None): + """Draw random samples from a matrix normal distribution. + + Parameters + ---------- + %(_matnorm_doc_default_callparams)s + size : integer, optional + Number of samples to draw (default 1). + %(_doc_random_state)s + + Returns + ------- + rvs : ndarray or scalar + Random variates of size (`size`, `dims`), where `dims` is the + dimension of the random matrices. + + Notes + ----- + %(_matnorm_doc_callparams_note)s + + """ + size = int(size) + dims, mean, rowcov, colcov = self._process_parameters(mean, rowcov, + colcov) + rowchol = scipy.linalg.cholesky(rowcov, lower=True) + colchol = scipy.linalg.cholesky(colcov, lower=True) + random_state = self._get_random_state(random_state) + # We aren't generating standard normal variates with size=(size, + # dims[0], dims[1]) directly to ensure random variates remain backwards + # compatible. See https://github.com/scipy/scipy/pull/12312 for more + # details. + std_norm = random_state.standard_normal( + size=(dims[1], size, dims[0]) + ).transpose(1, 2, 0) + out = mean + np.einsum('jp,ipq,kq->ijk', + rowchol, std_norm, colchol, + optimize=True) + if size == 1: + out = out.reshape(mean.shape) + return out + + def entropy(self, rowcov=1, colcov=1): + """Log of the matrix normal probability density function. + + Parameters + ---------- + rowcov : array_like, optional + Among-row covariance matrix of the distribution (default: `1`) + colcov : array_like, optional + Among-column covariance matrix of the distribution (default: `1`) + + Returns + ------- + entropy : float + Entropy of the distribution + + Notes + ----- + %(_matnorm_doc_callparams_note)s + + """ + dummy_mean = np.zeros((rowcov.shape[0], colcov.shape[0])) + dims, _, rowcov, colcov = self._process_parameters(dummy_mean, + rowcov, + colcov) + rowpsd = _PSD(rowcov, allow_singular=False) + colpsd = _PSD(colcov, allow_singular=False) + + return self._entropy(dims, rowpsd.log_pdet, colpsd.log_pdet) + + def _entropy(self, dims, row_cov_logdet, col_cov_logdet): + n, p = dims + return (0.5 * n * p * (1 + _LOG_2PI) + 0.5 * p * row_cov_logdet + + 0.5 * n * col_cov_logdet) + + +matrix_normal = matrix_normal_gen() + + +class matrix_normal_frozen(multi_rv_frozen): + """ + Create a frozen matrix normal distribution. + + Parameters + ---------- + %(_matnorm_doc_default_callparams)s + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is `None` the `~np.random.RandomState` singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, seeded + with seed. + If `seed` is already a ``RandomState`` or ``Generator`` instance, + then that object is used. + Default is `None`. + + Examples + -------- + >>> import numpy as np + >>> from scipy.stats import matrix_normal + + >>> distn = matrix_normal(mean=np.zeros((3,3))) + >>> X = distn.rvs(); X + array([[-0.02976962, 0.93339138, -0.09663178], + [ 0.67405524, 0.28250467, -0.93308929], + [-0.31144782, 0.74535536, 1.30412916]]) + >>> distn.pdf(X) + 2.5160642368346784e-05 + >>> distn.logpdf(X) + -10.590229595124615 + """ + + def __init__(self, mean=None, rowcov=1, colcov=1, seed=None): + self._dist = matrix_normal_gen(seed) + self.dims, self.mean, self.rowcov, self.colcov = \ + self._dist._process_parameters(mean, rowcov, colcov) + self.rowpsd = _PSD(self.rowcov, allow_singular=False) + self.colpsd = _PSD(self.colcov, allow_singular=False) + + def logpdf(self, X): + X = self._dist._process_quantiles(X, self.dims) + out = self._dist._logpdf(self.dims, X, self.mean, self.rowpsd.U, + self.rowpsd.log_pdet, self.colpsd.U, + self.colpsd.log_pdet) + return _squeeze_output(out) + + def pdf(self, X): + return np.exp(self.logpdf(X)) + + def rvs(self, size=1, random_state=None): + return self._dist.rvs(self.mean, self.rowcov, self.colcov, size, + random_state) + + def entropy(self): + return self._dist._entropy(self.dims, self.rowpsd.log_pdet, + self.colpsd.log_pdet) + + +# Set frozen generator docstrings from corresponding docstrings in +# matrix_normal_gen and fill in default strings in class docstrings +for name in ['logpdf', 'pdf', 'rvs', 'entropy']: + method = matrix_normal_gen.__dict__[name] + method_frozen = matrix_normal_frozen.__dict__[name] + method_frozen.__doc__ = doccer.docformat(method.__doc__, + matnorm_docdict_noparams) + method.__doc__ = doccer.docformat(method.__doc__, matnorm_docdict_params) + +_dirichlet_doc_default_callparams = """\ +alpha : array_like + The concentration parameters. The number of entries determines the + dimensionality of the distribution. +""" +_dirichlet_doc_frozen_callparams = "" + +_dirichlet_doc_frozen_callparams_note = """\ +See class definition for a detailed description of parameters.""" + +dirichlet_docdict_params = { + '_dirichlet_doc_default_callparams': _dirichlet_doc_default_callparams, + '_doc_random_state': _doc_random_state +} + +dirichlet_docdict_noparams = { + '_dirichlet_doc_default_callparams': _dirichlet_doc_frozen_callparams, + '_doc_random_state': _doc_random_state +} + + +def _dirichlet_check_parameters(alpha): + alpha = np.asarray(alpha) + if np.min(alpha) <= 0: + raise ValueError("All parameters must be greater than 0") + elif alpha.ndim != 1: + raise ValueError("Parameter vector 'a' must be one dimensional, " + f"but a.shape = {alpha.shape}.") + return alpha + + +def _dirichlet_check_input(alpha, x): + x = np.asarray(x) + + if x.shape[0] + 1 != alpha.shape[0] and x.shape[0] != alpha.shape[0]: + raise ValueError("Vector 'x' must have either the same number " + "of entries as, or one entry fewer than, " + f"parameter vector 'a', but alpha.shape = {alpha.shape} " + f"and x.shape = {x.shape}.") + + if x.shape[0] != alpha.shape[0]: + xk = np.array([1 - np.sum(x, 0)]) + if xk.ndim == 1: + x = np.append(x, xk) + elif xk.ndim == 2: + x = np.vstack((x, xk)) + else: + raise ValueError("The input must be one dimensional or a two " + "dimensional matrix containing the entries.") + + if np.min(x) < 0: + raise ValueError("Each entry in 'x' must be greater than or equal " + "to zero.") + + if np.max(x) > 1: + raise ValueError("Each entry in 'x' must be smaller or equal one.") + + # Check x_i > 0 or alpha_i > 1 + xeq0 = (x == 0) + alphalt1 = (alpha < 1) + if x.shape != alpha.shape: + alphalt1 = np.repeat(alphalt1, x.shape[-1], axis=-1).reshape(x.shape) + chk = np.logical_and(xeq0, alphalt1) + + if np.sum(chk): + raise ValueError("Each entry in 'x' must be greater than zero if its " + "alpha is less than one.") + + if (np.abs(np.sum(x, 0) - 1.0) > 10e-10).any(): + raise ValueError("The input vector 'x' must lie within the normal " + "simplex. but np.sum(x, 0) = %s." % np.sum(x, 0)) + + return x + + +def _lnB(alpha): + r"""Internal helper function to compute the log of the useful quotient. + + .. math:: + + B(\alpha) = \frac{\prod_{i=1}{K}\Gamma(\alpha_i)} + {\Gamma\left(\sum_{i=1}^{K} \alpha_i \right)} + + Parameters + ---------- + %(_dirichlet_doc_default_callparams)s + + Returns + ------- + B : scalar + Helper quotient, internal use only + + """ + return np.sum(gammaln(alpha)) - gammaln(np.sum(alpha)) + + +class dirichlet_gen(multi_rv_generic): + r"""A Dirichlet random variable. + + The ``alpha`` keyword specifies the concentration parameters of the + distribution. + + .. versionadded:: 0.15.0 + + Methods + ------- + pdf(x, alpha) + Probability density function. + logpdf(x, alpha) + Log of the probability density function. + rvs(alpha, size=1, random_state=None) + Draw random samples from a Dirichlet distribution. + mean(alpha) + The mean of the Dirichlet distribution + var(alpha) + The variance of the Dirichlet distribution + cov(alpha) + The covariance of the Dirichlet distribution + entropy(alpha) + Compute the differential entropy of the Dirichlet distribution. + + Parameters + ---------- + %(_dirichlet_doc_default_callparams)s + %(_doc_random_state)s + + Notes + ----- + Each :math:`\alpha` entry must be positive. The distribution has only + support on the simplex defined by + + .. math:: + \sum_{i=1}^{K} x_i = 1 + + where :math:`0 < x_i < 1`. + + If the quantiles don't lie within the simplex, a ValueError is raised. + + The probability density function for `dirichlet` is + + .. math:: + + f(x) = \frac{1}{\mathrm{B}(\boldsymbol\alpha)} \prod_{i=1}^K x_i^{\alpha_i - 1} + + where + + .. math:: + + \mathrm{B}(\boldsymbol\alpha) = \frac{\prod_{i=1}^K \Gamma(\alpha_i)} + {\Gamma\bigl(\sum_{i=1}^K \alpha_i\bigr)} + + and :math:`\boldsymbol\alpha=(\alpha_1,\ldots,\alpha_K)`, the + concentration parameters and :math:`K` is the dimension of the space + where :math:`x` takes values. + + Note that the `dirichlet` interface is somewhat inconsistent. + The array returned by the rvs function is transposed + with respect to the format expected by the pdf and logpdf. + + Examples + -------- + >>> import numpy as np + >>> from scipy.stats import dirichlet + + Generate a dirichlet random variable + + >>> quantiles = np.array([0.2, 0.2, 0.6]) # specify quantiles + >>> alpha = np.array([0.4, 5, 15]) # specify concentration parameters + >>> dirichlet.pdf(quantiles, alpha) + 0.2843831684937255 + + The same PDF but following a log scale + + >>> dirichlet.logpdf(quantiles, alpha) + -1.2574327653159187 + + Once we specify the dirichlet distribution + we can then calculate quantities of interest + + >>> dirichlet.mean(alpha) # get the mean of the distribution + array([0.01960784, 0.24509804, 0.73529412]) + >>> dirichlet.var(alpha) # get variance + array([0.00089829, 0.00864603, 0.00909517]) + >>> dirichlet.entropy(alpha) # calculate the differential entropy + -4.3280162474082715 + + We can also return random samples from the distribution + + >>> dirichlet.rvs(alpha, size=1, random_state=1) + array([[0.00766178, 0.24670518, 0.74563305]]) + >>> dirichlet.rvs(alpha, size=2, random_state=2) + array([[0.01639427, 0.1292273 , 0.85437844], + [0.00156917, 0.19033695, 0.80809388]]) + + Alternatively, the object may be called (as a function) to fix + concentration parameters, returning a "frozen" Dirichlet + random variable: + + >>> rv = dirichlet(alpha) + >>> # Frozen object with the same methods but holding the given + >>> # concentration parameters fixed. + + """ + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__, dirichlet_docdict_params) + + def __call__(self, alpha, seed=None): + return dirichlet_frozen(alpha, seed=seed) + + def _logpdf(self, x, alpha): + """Log of the Dirichlet probability density function. + + Parameters + ---------- + x : ndarray + Points at which to evaluate the log of the probability + density function + %(_dirichlet_doc_default_callparams)s + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'logpdf' instead. + + """ + lnB = _lnB(alpha) + return - lnB + np.sum((xlogy(alpha - 1, x.T)).T, 0) + + def logpdf(self, x, alpha): + """Log of the Dirichlet probability density function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + %(_dirichlet_doc_default_callparams)s + + Returns + ------- + pdf : ndarray or scalar + Log of the probability density function evaluated at `x`. + + """ + alpha = _dirichlet_check_parameters(alpha) + x = _dirichlet_check_input(alpha, x) + + out = self._logpdf(x, alpha) + return _squeeze_output(out) + + def pdf(self, x, alpha): + """The Dirichlet probability density function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + %(_dirichlet_doc_default_callparams)s + + Returns + ------- + pdf : ndarray or scalar + The probability density function evaluated at `x`. + + """ + alpha = _dirichlet_check_parameters(alpha) + x = _dirichlet_check_input(alpha, x) + + out = np.exp(self._logpdf(x, alpha)) + return _squeeze_output(out) + + def mean(self, alpha): + """Mean of the Dirichlet distribution. + + Parameters + ---------- + %(_dirichlet_doc_default_callparams)s + + Returns + ------- + mu : ndarray or scalar + Mean of the Dirichlet distribution. + + """ + alpha = _dirichlet_check_parameters(alpha) + + out = alpha / (np.sum(alpha)) + return _squeeze_output(out) + + def var(self, alpha): + """Variance of the Dirichlet distribution. + + Parameters + ---------- + %(_dirichlet_doc_default_callparams)s + + Returns + ------- + v : ndarray or scalar + Variance of the Dirichlet distribution. + + """ + + alpha = _dirichlet_check_parameters(alpha) + + alpha0 = np.sum(alpha) + out = (alpha * (alpha0 - alpha)) / ((alpha0 * alpha0) * (alpha0 + 1)) + return _squeeze_output(out) + + def cov(self, alpha): + """Covariance matrix of the Dirichlet distribution. + + Parameters + ---------- + %(_dirichlet_doc_default_callparams)s + + Returns + ------- + cov : ndarray + The covariance matrix of the distribution. + """ + + alpha = _dirichlet_check_parameters(alpha) + alpha0 = np.sum(alpha) + a = alpha / alpha0 + + cov = (np.diag(a) - np.outer(a, a)) / (alpha0 + 1) + return _squeeze_output(cov) + + def entropy(self, alpha): + """ + Differential entropy of the Dirichlet distribution. + + Parameters + ---------- + %(_dirichlet_doc_default_callparams)s + + Returns + ------- + h : scalar + Entropy of the Dirichlet distribution + + """ + + alpha = _dirichlet_check_parameters(alpha) + + alpha0 = np.sum(alpha) + lnB = _lnB(alpha) + K = alpha.shape[0] + + out = lnB + (alpha0 - K) * scipy.special.psi(alpha0) - np.sum( + (alpha - 1) * scipy.special.psi(alpha)) + return _squeeze_output(out) + + def rvs(self, alpha, size=1, random_state=None): + """ + Draw random samples from a Dirichlet distribution. + + Parameters + ---------- + %(_dirichlet_doc_default_callparams)s + size : int, optional + Number of samples to draw (default 1). + %(_doc_random_state)s + + Returns + ------- + rvs : ndarray or scalar + Random variates of size (`size`, `N`), where `N` is the + dimension of the random variable. + + """ + alpha = _dirichlet_check_parameters(alpha) + random_state = self._get_random_state(random_state) + return random_state.dirichlet(alpha, size=size) + + +dirichlet = dirichlet_gen() + + +class dirichlet_frozen(multi_rv_frozen): + def __init__(self, alpha, seed=None): + self.alpha = _dirichlet_check_parameters(alpha) + self._dist = dirichlet_gen(seed) + + def logpdf(self, x): + return self._dist.logpdf(x, self.alpha) + + def pdf(self, x): + return self._dist.pdf(x, self.alpha) + + def mean(self): + return self._dist.mean(self.alpha) + + def var(self): + return self._dist.var(self.alpha) + + def cov(self): + return self._dist.cov(self.alpha) + + def entropy(self): + return self._dist.entropy(self.alpha) + + def rvs(self, size=1, random_state=None): + return self._dist.rvs(self.alpha, size, random_state) + + +# Set frozen generator docstrings from corresponding docstrings in +# multivariate_normal_gen and fill in default strings in class docstrings +for name in ['logpdf', 'pdf', 'rvs', 'mean', 'var', 'cov', 'entropy']: + method = dirichlet_gen.__dict__[name] + method_frozen = dirichlet_frozen.__dict__[name] + method_frozen.__doc__ = doccer.docformat( + method.__doc__, dirichlet_docdict_noparams) + method.__doc__ = doccer.docformat(method.__doc__, dirichlet_docdict_params) + + +_wishart_doc_default_callparams = """\ +df : int + Degrees of freedom, must be greater than or equal to dimension of the + scale matrix +scale : array_like + Symmetric positive definite scale matrix of the distribution +""" + +_wishart_doc_callparams_note = "" + +_wishart_doc_frozen_callparams = "" + +_wishart_doc_frozen_callparams_note = """\ +See class definition for a detailed description of parameters.""" + +wishart_docdict_params = { + '_doc_default_callparams': _wishart_doc_default_callparams, + '_doc_callparams_note': _wishart_doc_callparams_note, + '_doc_random_state': _doc_random_state +} + +wishart_docdict_noparams = { + '_doc_default_callparams': _wishart_doc_frozen_callparams, + '_doc_callparams_note': _wishart_doc_frozen_callparams_note, + '_doc_random_state': _doc_random_state +} + + +class wishart_gen(multi_rv_generic): + r"""A Wishart random variable. + + The `df` keyword specifies the degrees of freedom. The `scale` keyword + specifies the scale matrix, which must be symmetric and positive definite. + In this context, the scale matrix is often interpreted in terms of a + multivariate normal precision matrix (the inverse of the covariance + matrix). These arguments must satisfy the relationship + ``df > scale.ndim - 1``, but see notes on using the `rvs` method with + ``df < scale.ndim``. + + Methods + ------- + pdf(x, df, scale) + Probability density function. + logpdf(x, df, scale) + Log of the probability density function. + rvs(df, scale, size=1, random_state=None) + Draw random samples from a Wishart distribution. + entropy() + Compute the differential entropy of the Wishart distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + %(_doc_random_state)s + + Raises + ------ + scipy.linalg.LinAlgError + If the scale matrix `scale` is not positive definite. + + See Also + -------- + invwishart, chi2 + + Notes + ----- + %(_doc_callparams_note)s + + The scale matrix `scale` must be a symmetric positive definite + matrix. Singular matrices, including the symmetric positive semi-definite + case, are not supported. Symmetry is not checked; only the lower triangular + portion is used. + + The Wishart distribution is often denoted + + .. math:: + + W_p(\nu, \Sigma) + + where :math:`\nu` is the degrees of freedom and :math:`\Sigma` is the + :math:`p \times p` scale matrix. + + The probability density function for `wishart` has support over positive + definite matrices :math:`S`; if :math:`S \sim W_p(\nu, \Sigma)`, then + its PDF is given by: + + .. math:: + + f(S) = \frac{|S|^{\frac{\nu - p - 1}{2}}}{2^{ \frac{\nu p}{2} } + |\Sigma|^\frac{\nu}{2} \Gamma_p \left ( \frac{\nu}{2} \right )} + \exp\left( -tr(\Sigma^{-1} S) / 2 \right) + + If :math:`S \sim W_p(\nu, \Sigma)` (Wishart) then + :math:`S^{-1} \sim W_p^{-1}(\nu, \Sigma^{-1})` (inverse Wishart). + + If the scale matrix is 1-dimensional and equal to one, then the Wishart + distribution :math:`W_1(\nu, 1)` collapses to the :math:`\chi^2(\nu)` + distribution. + + The algorithm [2]_ implemented by the `rvs` method may + produce numerically singular matrices with :math:`p - 1 < \nu < p`; the + user may wish to check for this condition and generate replacement samples + as necessary. + + + .. versionadded:: 0.16.0 + + References + ---------- + .. [1] M.L. Eaton, "Multivariate Statistics: A Vector Space Approach", + Wiley, 1983. + .. [2] W.B. Smith and R.R. Hocking, "Algorithm AS 53: Wishart Variate + Generator", Applied Statistics, vol. 21, pp. 341-345, 1972. + + Examples + -------- + >>> import numpy as np + >>> import matplotlib.pyplot as plt + >>> from scipy.stats import wishart, chi2 + >>> x = np.linspace(1e-5, 8, 100) + >>> w = wishart.pdf(x, df=3, scale=1); w[:5] + array([ 0.00126156, 0.10892176, 0.14793434, 0.17400548, 0.1929669 ]) + >>> c = chi2.pdf(x, 3); c[:5] + array([ 0.00126156, 0.10892176, 0.14793434, 0.17400548, 0.1929669 ]) + >>> plt.plot(x, w) + >>> plt.show() + + The input quantiles can be any shape of array, as long as the last + axis labels the components. + + Alternatively, the object may be called (as a function) to fix the degrees + of freedom and scale parameters, returning a "frozen" Wishart random + variable: + + >>> rv = wishart(df=1, scale=1) + >>> # Frozen object with the same methods but holding the given + >>> # degrees of freedom and scale fixed. + + """ + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__, wishart_docdict_params) + + def __call__(self, df=None, scale=None, seed=None): + """Create a frozen Wishart distribution. + + See `wishart_frozen` for more information. + """ + return wishart_frozen(df, scale, seed) + + def _process_parameters(self, df, scale): + if scale is None: + scale = 1.0 + scale = np.asarray(scale, dtype=float) + + if scale.ndim == 0: + scale = scale[np.newaxis, np.newaxis] + elif scale.ndim == 1: + scale = np.diag(scale) + elif scale.ndim == 2 and not scale.shape[0] == scale.shape[1]: + raise ValueError("Array 'scale' must be square if it is two" + " dimensional, but scale.scale = %s." + % str(scale.shape)) + elif scale.ndim > 2: + raise ValueError("Array 'scale' must be at most two-dimensional," + " but scale.ndim = %d" % scale.ndim) + + dim = scale.shape[0] + + if df is None: + df = dim + elif not np.isscalar(df): + raise ValueError("Degrees of freedom must be a scalar.") + elif df <= dim - 1: + raise ValueError("Degrees of freedom must be greater than the " + "dimension of scale matrix minus 1.") + + return dim, df, scale + + def _process_quantiles(self, x, dim): + """ + Adjust quantiles array so that last axis labels the components of + each data point. + """ + x = np.asarray(x, dtype=float) + + if x.ndim == 0: + x = x * np.eye(dim)[:, :, np.newaxis] + if x.ndim == 1: + if dim == 1: + x = x[np.newaxis, np.newaxis, :] + else: + x = np.diag(x)[:, :, np.newaxis] + elif x.ndim == 2: + if not x.shape[0] == x.shape[1]: + raise ValueError("Quantiles must be square if they are two" + " dimensional, but x.shape = %s." + % str(x.shape)) + x = x[:, :, np.newaxis] + elif x.ndim == 3: + if not x.shape[0] == x.shape[1]: + raise ValueError("Quantiles must be square in the first two" + " dimensions if they are three dimensional" + ", but x.shape = %s." % str(x.shape)) + elif x.ndim > 3: + raise ValueError("Quantiles must be at most two-dimensional with" + " an additional dimension for multiple" + "components, but x.ndim = %d" % x.ndim) + + # Now we have 3-dim array; should have shape [dim, dim, *] + if not x.shape[0:2] == (dim, dim): + raise ValueError('Quantiles have incompatible dimensions: should' + f' be {(dim, dim)}, got {x.shape[0:2]}.') + + return x + + def _process_size(self, size): + size = np.asarray(size) + + if size.ndim == 0: + size = size[np.newaxis] + elif size.ndim > 1: + raise ValueError('Size must be an integer or tuple of integers;' + ' thus must have dimension <= 1.' + ' Got size.ndim = %s' % str(tuple(size))) + n = size.prod() + shape = tuple(size) + + return n, shape + + def _logpdf(self, x, dim, df, scale, log_det_scale, C): + """Log of the Wishart probability density function. + + Parameters + ---------- + x : ndarray + Points at which to evaluate the log of the probability + density function + dim : int + Dimension of the scale matrix + df : int + Degrees of freedom + scale : ndarray + Scale matrix + log_det_scale : float + Logarithm of the determinant of the scale matrix + C : ndarray + Cholesky factorization of the scale matrix, lower triagular. + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'logpdf' instead. + + """ + # log determinant of x + # Note: x has components along the last axis, so that x.T has + # components alone the 0-th axis. Then since det(A) = det(A'), this + # gives us a 1-dim vector of determinants + + # Retrieve tr(scale^{-1} x) + log_det_x = np.empty(x.shape[-1]) + scale_inv_x = np.empty(x.shape) + tr_scale_inv_x = np.empty(x.shape[-1]) + for i in range(x.shape[-1]): + _, log_det_x[i] = self._cholesky_logdet(x[:, :, i]) + scale_inv_x[:, :, i] = scipy.linalg.cho_solve((C, True), x[:, :, i]) + tr_scale_inv_x[i] = scale_inv_x[:, :, i].trace() + + # Log PDF + out = ((0.5 * (df - dim - 1) * log_det_x - 0.5 * tr_scale_inv_x) - + (0.5 * df * dim * _LOG_2 + 0.5 * df * log_det_scale + + multigammaln(0.5*df, dim))) + + return out + + def logpdf(self, x, df, scale): + """Log of the Wishart probability density function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + Each quantile must be a symmetric positive definite matrix. + %(_doc_default_callparams)s + + Returns + ------- + pdf : ndarray + Log of the probability density function evaluated at `x` + + Notes + ----- + %(_doc_callparams_note)s + + """ + dim, df, scale = self._process_parameters(df, scale) + x = self._process_quantiles(x, dim) + + # Cholesky decomposition of scale, get log(det(scale)) + C, log_det_scale = self._cholesky_logdet(scale) + + out = self._logpdf(x, dim, df, scale, log_det_scale, C) + return _squeeze_output(out) + + def pdf(self, x, df, scale): + """Wishart probability density function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + Each quantile must be a symmetric positive definite matrix. + %(_doc_default_callparams)s + + Returns + ------- + pdf : ndarray + Probability density function evaluated at `x` + + Notes + ----- + %(_doc_callparams_note)s + + """ + return np.exp(self.logpdf(x, df, scale)) + + def _mean(self, dim, df, scale): + """Mean of the Wishart distribution. + + Parameters + ---------- + dim : int + Dimension of the scale matrix + %(_doc_default_callparams)s + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'mean' instead. + + """ + return df * scale + + def mean(self, df, scale): + """Mean of the Wishart distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + mean : float + The mean of the distribution + """ + dim, df, scale = self._process_parameters(df, scale) + out = self._mean(dim, df, scale) + return _squeeze_output(out) + + def _mode(self, dim, df, scale): + """Mode of the Wishart distribution. + + Parameters + ---------- + dim : int + Dimension of the scale matrix + %(_doc_default_callparams)s + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'mode' instead. + + """ + if df >= dim + 1: + out = (df-dim-1) * scale + else: + out = None + return out + + def mode(self, df, scale): + """Mode of the Wishart distribution + + Only valid if the degrees of freedom are greater than the dimension of + the scale matrix. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + mode : float or None + The Mode of the distribution + """ + dim, df, scale = self._process_parameters(df, scale) + out = self._mode(dim, df, scale) + return _squeeze_output(out) if out is not None else out + + def _var(self, dim, df, scale): + """Variance of the Wishart distribution. + + Parameters + ---------- + dim : int + Dimension of the scale matrix + %(_doc_default_callparams)s + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'var' instead. + + """ + var = scale**2 + diag = scale.diagonal() # 1 x dim array + var += np.outer(diag, diag) + var *= df + return var + + def var(self, df, scale): + """Variance of the Wishart distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + var : float + The variance of the distribution + """ + dim, df, scale = self._process_parameters(df, scale) + out = self._var(dim, df, scale) + return _squeeze_output(out) + + def _standard_rvs(self, n, shape, dim, df, random_state): + """ + Parameters + ---------- + n : integer + Number of variates to generate + shape : iterable + Shape of the variates to generate + dim : int + Dimension of the scale matrix + df : int + Degrees of freedom + random_state : {None, int, `numpy.random.Generator`, + `numpy.random.RandomState`}, optional + + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'rvs' instead. + + """ + # Random normal variates for off-diagonal elements + n_tril = dim * (dim-1) // 2 + covariances = random_state.normal( + size=n*n_tril).reshape(shape+(n_tril,)) + + # Random chi-square variates for diagonal elements + variances = (np.r_[[random_state.chisquare(df-(i+1)+1, size=n)**0.5 + for i in range(dim)]].reshape((dim,) + + shape[::-1]).T) + + # Create the A matri(ces) - lower triangular + A = np.zeros(shape + (dim, dim)) + + # Input the covariances + size_idx = tuple([slice(None, None, None)]*len(shape)) + tril_idx = np.tril_indices(dim, k=-1) + A[size_idx + tril_idx] = covariances + + # Input the variances + diag_idx = np.diag_indices(dim) + A[size_idx + diag_idx] = variances + + return A + + def _rvs(self, n, shape, dim, df, C, random_state): + """Draw random samples from a Wishart distribution. + + Parameters + ---------- + n : integer + Number of variates to generate + shape : iterable + Shape of the variates to generate + dim : int + Dimension of the scale matrix + df : int + Degrees of freedom + C : ndarray + Cholesky factorization of the scale matrix, lower triangular. + %(_doc_random_state)s + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'rvs' instead. + + """ + random_state = self._get_random_state(random_state) + # Calculate the matrices A, which are actually lower triangular + # Cholesky factorizations of a matrix B such that B ~ W(df, I) + A = self._standard_rvs(n, shape, dim, df, random_state) + + # Calculate SA = C A A' C', where SA ~ W(df, scale) + # Note: this is the product of a (lower) (lower) (lower)' (lower)' + # or, denoting B = AA', it is C B C' where C is the lower + # triangular Cholesky factorization of the scale matrix. + # this appears to conflict with the instructions in [1]_, which + # suggest that it should be D' B D where D is the lower + # triangular factorization of the scale matrix. However, it is + # meant to refer to the Bartlett (1933) representation of a + # Wishart random variate as L A A' L' where L is lower triangular + # so it appears that understanding D' to be upper triangular + # is either a typo in or misreading of [1]_. + for index in np.ndindex(shape): + CA = np.dot(C, A[index]) + A[index] = np.dot(CA, CA.T) + + return A + + def rvs(self, df, scale, size=1, random_state=None): + """Draw random samples from a Wishart distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + size : integer or iterable of integers, optional + Number of samples to draw (default 1). + %(_doc_random_state)s + + Returns + ------- + rvs : ndarray + Random variates of shape (`size`) + (``dim``, ``dim``), where + ``dim`` is the dimension of the scale matrix. + + Notes + ----- + %(_doc_callparams_note)s + + """ + n, shape = self._process_size(size) + dim, df, scale = self._process_parameters(df, scale) + + # Cholesky decomposition of scale + C = scipy.linalg.cholesky(scale, lower=True) + + out = self._rvs(n, shape, dim, df, C, random_state) + + return _squeeze_output(out) + + def _entropy(self, dim, df, log_det_scale): + """Compute the differential entropy of the Wishart. + + Parameters + ---------- + dim : int + Dimension of the scale matrix + df : int + Degrees of freedom + log_det_scale : float + Logarithm of the determinant of the scale matrix + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'entropy' instead. + + """ + return ( + 0.5 * (dim+1) * log_det_scale + + 0.5 * dim * (dim+1) * _LOG_2 + + multigammaln(0.5*df, dim) - + 0.5 * (df - dim - 1) * np.sum( + [psi(0.5*(df + 1 - (i+1))) for i in range(dim)] + ) + + 0.5 * df * dim + ) + + def entropy(self, df, scale): + """Compute the differential entropy of the Wishart. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + h : scalar + Entropy of the Wishart distribution + + Notes + ----- + %(_doc_callparams_note)s + + """ + dim, df, scale = self._process_parameters(df, scale) + _, log_det_scale = self._cholesky_logdet(scale) + return self._entropy(dim, df, log_det_scale) + + def _cholesky_logdet(self, scale): + """Compute Cholesky decomposition and determine (log(det(scale)). + + Parameters + ---------- + scale : ndarray + Scale matrix. + + Returns + ------- + c_decomp : ndarray + The Cholesky decomposition of `scale`. + logdet : scalar + The log of the determinant of `scale`. + + Notes + ----- + This computation of ``logdet`` is equivalent to + ``np.linalg.slogdet(scale)``. It is ~2x faster though. + + """ + c_decomp = scipy.linalg.cholesky(scale, lower=True) + logdet = 2 * np.sum(np.log(c_decomp.diagonal())) + return c_decomp, logdet + + +wishart = wishart_gen() + + +class wishart_frozen(multi_rv_frozen): + """Create a frozen Wishart distribution. + + Parameters + ---------- + df : array_like + Degrees of freedom of the distribution + scale : array_like + Scale matrix of the distribution + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance then + that instance is used. + + """ + def __init__(self, df, scale, seed=None): + self._dist = wishart_gen(seed) + self.dim, self.df, self.scale = self._dist._process_parameters( + df, scale) + self.C, self.log_det_scale = self._dist._cholesky_logdet(self.scale) + + def logpdf(self, x): + x = self._dist._process_quantiles(x, self.dim) + + out = self._dist._logpdf(x, self.dim, self.df, self.scale, + self.log_det_scale, self.C) + return _squeeze_output(out) + + def pdf(self, x): + return np.exp(self.logpdf(x)) + + def mean(self): + out = self._dist._mean(self.dim, self.df, self.scale) + return _squeeze_output(out) + + def mode(self): + out = self._dist._mode(self.dim, self.df, self.scale) + return _squeeze_output(out) if out is not None else out + + def var(self): + out = self._dist._var(self.dim, self.df, self.scale) + return _squeeze_output(out) + + def rvs(self, size=1, random_state=None): + n, shape = self._dist._process_size(size) + out = self._dist._rvs(n, shape, self.dim, self.df, + self.C, random_state) + return _squeeze_output(out) + + def entropy(self): + return self._dist._entropy(self.dim, self.df, self.log_det_scale) + + +# Set frozen generator docstrings from corresponding docstrings in +# Wishart and fill in default strings in class docstrings +for name in ['logpdf', 'pdf', 'mean', 'mode', 'var', 'rvs', 'entropy']: + method = wishart_gen.__dict__[name] + method_frozen = wishart_frozen.__dict__[name] + method_frozen.__doc__ = doccer.docformat( + method.__doc__, wishart_docdict_noparams) + method.__doc__ = doccer.docformat(method.__doc__, wishart_docdict_params) + + +class invwishart_gen(wishart_gen): + r"""An inverse Wishart random variable. + + The `df` keyword specifies the degrees of freedom. The `scale` keyword + specifies the scale matrix, which must be symmetric and positive definite. + In this context, the scale matrix is often interpreted in terms of a + multivariate normal covariance matrix. + + Methods + ------- + pdf(x, df, scale) + Probability density function. + logpdf(x, df, scale) + Log of the probability density function. + rvs(df, scale, size=1, random_state=None) + Draw random samples from an inverse Wishart distribution. + entropy(df, scale) + Differential entropy of the distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + %(_doc_random_state)s + + Raises + ------ + scipy.linalg.LinAlgError + If the scale matrix `scale` is not positive definite. + + See Also + -------- + wishart + + Notes + ----- + %(_doc_callparams_note)s + + The scale matrix `scale` must be a symmetric positive definite + matrix. Singular matrices, including the symmetric positive semi-definite + case, are not supported. Symmetry is not checked; only the lower triangular + portion is used. + + The inverse Wishart distribution is often denoted + + .. math:: + + W_p^{-1}(\nu, \Psi) + + where :math:`\nu` is the degrees of freedom and :math:`\Psi` is the + :math:`p \times p` scale matrix. + + The probability density function for `invwishart` has support over positive + definite matrices :math:`S`; if :math:`S \sim W^{-1}_p(\nu, \Sigma)`, + then its PDF is given by: + + .. math:: + + f(S) = \frac{|\Sigma|^\frac{\nu}{2}}{2^{ \frac{\nu p}{2} } + |S|^{\frac{\nu + p + 1}{2}} \Gamma_p \left(\frac{\nu}{2} \right)} + \exp\left( -tr(\Sigma S^{-1}) / 2 \right) + + If :math:`S \sim W_p^{-1}(\nu, \Psi)` (inverse Wishart) then + :math:`S^{-1} \sim W_p(\nu, \Psi^{-1})` (Wishart). + + If the scale matrix is 1-dimensional and equal to one, then the inverse + Wishart distribution :math:`W_1(\nu, 1)` collapses to the + inverse Gamma distribution with parameters shape = :math:`\frac{\nu}{2}` + and scale = :math:`\frac{1}{2}`. + + Instead of inverting a randomly generated Wishart matrix as described in [2], + here the algorithm in [4] is used to directly generate a random inverse-Wishart + matrix without inversion. + + .. versionadded:: 0.16.0 + + References + ---------- + .. [1] M.L. Eaton, "Multivariate Statistics: A Vector Space Approach", + Wiley, 1983. + .. [2] M.C. Jones, "Generating Inverse Wishart Matrices", Communications + in Statistics - Simulation and Computation, vol. 14.2, pp.511-514, + 1985. + .. [3] Gupta, M. and Srivastava, S. "Parametric Bayesian Estimation of + Differential Entropy and Relative Entropy". Entropy 12, 818 - 843. + 2010. + .. [4] S.D. Axen, "Efficiently generating inverse-Wishart matrices and + their Cholesky factors", :arXiv:`2310.15884v1`. 2023. + + Examples + -------- + >>> import numpy as np + >>> import matplotlib.pyplot as plt + >>> from scipy.stats import invwishart, invgamma + >>> x = np.linspace(0.01, 1, 100) + >>> iw = invwishart.pdf(x, df=6, scale=1) + >>> iw[:3] + array([ 1.20546865e-15, 5.42497807e-06, 4.45813929e-03]) + >>> ig = invgamma.pdf(x, 6/2., scale=1./2) + >>> ig[:3] + array([ 1.20546865e-15, 5.42497807e-06, 4.45813929e-03]) + >>> plt.plot(x, iw) + >>> plt.show() + + The input quantiles can be any shape of array, as long as the last + axis labels the components. + + Alternatively, the object may be called (as a function) to fix the degrees + of freedom and scale parameters, returning a "frozen" inverse Wishart + random variable: + + >>> rv = invwishart(df=1, scale=1) + >>> # Frozen object with the same methods but holding the given + >>> # degrees of freedom and scale fixed. + + """ + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__, wishart_docdict_params) + + def __call__(self, df=None, scale=None, seed=None): + """Create a frozen inverse Wishart distribution. + + See `invwishart_frozen` for more information. + + """ + return invwishart_frozen(df, scale, seed) + + def _logpdf(self, x, dim, df, log_det_scale, C): + """Log of the inverse Wishart probability density function. + + Parameters + ---------- + x : ndarray + Points at which to evaluate the log of the probability + density function. + dim : int + Dimension of the scale matrix + df : int + Degrees of freedom + log_det_scale : float + Logarithm of the determinant of the scale matrix + C : ndarray + Cholesky factorization of the scale matrix, lower triagular. + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'logpdf' instead. + + """ + # Retrieve tr(scale x^{-1}) + log_det_x = np.empty(x.shape[-1]) + tr_scale_x_inv = np.empty(x.shape[-1]) + trsm = get_blas_funcs(('trsm'), (x,)) + if dim > 1: + for i in range(x.shape[-1]): + Cx, log_det_x[i] = self._cholesky_logdet(x[:, :, i]) + A = trsm(1., Cx, C, side=0, lower=True) + tr_scale_x_inv[i] = np.linalg.norm(A)**2 + else: + log_det_x[:] = np.log(x[0, 0]) + tr_scale_x_inv[:] = C[0, 0]**2 / x[0, 0] + + # Log PDF + out = ((0.5 * df * log_det_scale - 0.5 * tr_scale_x_inv) - + (0.5 * df * dim * _LOG_2 + 0.5 * (df + dim + 1) * log_det_x) - + multigammaln(0.5*df, dim)) + + return out + + def logpdf(self, x, df, scale): + """Log of the inverse Wishart probability density function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + Each quantile must be a symmetric positive definite matrix. + %(_doc_default_callparams)s + + Returns + ------- + pdf : ndarray + Log of the probability density function evaluated at `x` + + Notes + ----- + %(_doc_callparams_note)s + + """ + dim, df, scale = self._process_parameters(df, scale) + x = self._process_quantiles(x, dim) + C, log_det_scale = self._cholesky_logdet(scale) + out = self._logpdf(x, dim, df, log_det_scale, C) + return _squeeze_output(out) + + def pdf(self, x, df, scale): + """Inverse Wishart probability density function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + Each quantile must be a symmetric positive definite matrix. + %(_doc_default_callparams)s + + Returns + ------- + pdf : ndarray + Probability density function evaluated at `x` + + Notes + ----- + %(_doc_callparams_note)s + + """ + return np.exp(self.logpdf(x, df, scale)) + + def _mean(self, dim, df, scale): + """Mean of the inverse Wishart distribution. + + Parameters + ---------- + dim : int + Dimension of the scale matrix + %(_doc_default_callparams)s + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'mean' instead. + + """ + if df > dim + 1: + out = scale / (df - dim - 1) + else: + out = None + return out + + def mean(self, df, scale): + """Mean of the inverse Wishart distribution. + + Only valid if the degrees of freedom are greater than the dimension of + the scale matrix plus one. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + mean : float or None + The mean of the distribution + + """ + dim, df, scale = self._process_parameters(df, scale) + out = self._mean(dim, df, scale) + return _squeeze_output(out) if out is not None else out + + def _mode(self, dim, df, scale): + """Mode of the inverse Wishart distribution. + + Parameters + ---------- + dim : int + Dimension of the scale matrix + %(_doc_default_callparams)s + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'mode' instead. + + """ + return scale / (df + dim + 1) + + def mode(self, df, scale): + """Mode of the inverse Wishart distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + mode : float + The Mode of the distribution + + """ + dim, df, scale = self._process_parameters(df, scale) + out = self._mode(dim, df, scale) + return _squeeze_output(out) + + def _var(self, dim, df, scale): + """Variance of the inverse Wishart distribution. + + Parameters + ---------- + dim : int + Dimension of the scale matrix + %(_doc_default_callparams)s + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'var' instead. + + """ + if df > dim + 3: + var = (df - dim + 1) * scale**2 + diag = scale.diagonal() # 1 x dim array + var += (df - dim - 1) * np.outer(diag, diag) + var /= (df - dim) * (df - dim - 1)**2 * (df - dim - 3) + else: + var = None + return var + + def var(self, df, scale): + """Variance of the inverse Wishart distribution. + + Only valid if the degrees of freedom are greater than the dimension of + the scale matrix plus three. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + var : float + The variance of the distribution + """ + dim, df, scale = self._process_parameters(df, scale) + out = self._var(dim, df, scale) + return _squeeze_output(out) if out is not None else out + + def _inv_standard_rvs(self, n, shape, dim, df, random_state): + """ + Parameters + ---------- + n : integer + Number of variates to generate + shape : iterable + Shape of the variates to generate + dim : int + Dimension of the scale matrix + df : int + Degrees of freedom + random_state : {None, int, `numpy.random.Generator`, + `numpy.random.RandomState`}, optional + + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + + Returns + ------- + A : ndarray + Random variates of shape (`shape`) + (``dim``, ``dim``). + Each slice `A[..., :, :]` is lower-triangular, and its + inverse is the lower Cholesky factor of a draw from + `invwishart(df, np.eye(dim))`. + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'rvs' instead. + + """ + A = np.zeros(shape + (dim, dim)) + + # Random normal variates for off-diagonal elements + tri_rows, tri_cols = np.tril_indices(dim, k=-1) + n_tril = dim * (dim-1) // 2 + A[..., tri_rows, tri_cols] = random_state.normal( + size=(*shape, n_tril), + ) + + # Random chi variates for diagonal elements + rows = np.arange(dim) + chi_dfs = (df - dim + 1) + rows + A[..., rows, rows] = random_state.chisquare( + df=chi_dfs, size=(*shape, dim), + )**0.5 + + return A + + def _rvs(self, n, shape, dim, df, C, random_state): + """Draw random samples from an inverse Wishart distribution. + + Parameters + ---------- + n : integer + Number of variates to generate + shape : iterable + Shape of the variates to generate + dim : int + Dimension of the scale matrix + df : int + Degrees of freedom + C : ndarray + Cholesky factorization of the scale matrix, lower triagular. + %(_doc_random_state)s + + Notes + ----- + As this function does no argument checking, it should not be + called directly; use 'rvs' instead. + + """ + random_state = self._get_random_state(random_state) + # Get random draws A such that inv(A) ~ iW(df, I) + A = self._inv_standard_rvs(n, shape, dim, df, random_state) + + # Calculate SA = (CA)'^{-1} (CA)^{-1} ~ iW(df, scale) + trsm = get_blas_funcs(('trsm'), (A,)) + trmm = get_blas_funcs(('trmm'), (A,)) + + for index in np.ndindex(A.shape[:-2]): + if dim > 1: + # Calculate CA + # Get CA = C A^{-1} via triangular solver + CA = trsm(1., A[index], C, side=1, lower=True) + # get SA + A[index] = trmm(1., CA, CA, side=1, lower=True, trans_a=True) + else: + A[index][0, 0] = (C[0, 0] / A[index][0, 0])**2 + + return A + + def rvs(self, df, scale, size=1, random_state=None): + """Draw random samples from an inverse Wishart distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + size : integer or iterable of integers, optional + Number of samples to draw (default 1). + %(_doc_random_state)s + + Returns + ------- + rvs : ndarray + Random variates of shape (`size`) + (``dim``, ``dim``), where + ``dim`` is the dimension of the scale matrix. + + Notes + ----- + %(_doc_callparams_note)s + + """ + n, shape = self._process_size(size) + dim, df, scale = self._process_parameters(df, scale) + + # Cholesky decomposition of scale + C = scipy.linalg.cholesky(scale, lower=True) + + out = self._rvs(n, shape, dim, df, C, random_state) + + return _squeeze_output(out) + + def _entropy(self, dim, df, log_det_scale): + # reference: eq. (17) from ref. 3 + psi_eval_points = [0.5 * (df - dim + i) for i in range(1, dim + 1)] + psi_eval_points = np.asarray(psi_eval_points) + return multigammaln(0.5 * df, dim) + 0.5 * dim * df + \ + 0.5 * (dim + 1) * (log_det_scale - _LOG_2) - \ + 0.5 * (df + dim + 1) * \ + psi(psi_eval_points, out=psi_eval_points).sum() + + def entropy(self, df, scale): + dim, df, scale = self._process_parameters(df, scale) + _, log_det_scale = self._cholesky_logdet(scale) + return self._entropy(dim, df, log_det_scale) + + +invwishart = invwishart_gen() + + +class invwishart_frozen(multi_rv_frozen): + def __init__(self, df, scale, seed=None): + """Create a frozen inverse Wishart distribution. + + Parameters + ---------- + df : array_like + Degrees of freedom of the distribution + scale : array_like + Scale matrix of the distribution + seed : {None, int, `numpy.random.Generator`}, optional + If `seed` is None the `numpy.random.Generator` singleton is used. + If `seed` is an int, a new ``Generator`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` instance then that instance is + used. + + """ + self._dist = invwishart_gen(seed) + self.dim, self.df, self.scale = self._dist._process_parameters( + df, scale + ) + + # Get the determinant via Cholesky factorization + self.C = scipy.linalg.cholesky(self.scale, lower=True) + self.log_det_scale = 2 * np.sum(np.log(self.C.diagonal())) + + def logpdf(self, x): + x = self._dist._process_quantiles(x, self.dim) + out = self._dist._logpdf(x, self.dim, self.df, + self.log_det_scale, self.C) + return _squeeze_output(out) + + def pdf(self, x): + return np.exp(self.logpdf(x)) + + def mean(self): + out = self._dist._mean(self.dim, self.df, self.scale) + return _squeeze_output(out) if out is not None else out + + def mode(self): + out = self._dist._mode(self.dim, self.df, self.scale) + return _squeeze_output(out) + + def var(self): + out = self._dist._var(self.dim, self.df, self.scale) + return _squeeze_output(out) if out is not None else out + + def rvs(self, size=1, random_state=None): + n, shape = self._dist._process_size(size) + + out = self._dist._rvs(n, shape, self.dim, self.df, + self.C, random_state) + + return _squeeze_output(out) + + def entropy(self): + return self._dist._entropy(self.dim, self.df, self.log_det_scale) + + +# Set frozen generator docstrings from corresponding docstrings in +# inverse Wishart and fill in default strings in class docstrings +for name in ['logpdf', 'pdf', 'mean', 'mode', 'var', 'rvs']: + method = invwishart_gen.__dict__[name] + method_frozen = wishart_frozen.__dict__[name] + method_frozen.__doc__ = doccer.docformat( + method.__doc__, wishart_docdict_noparams) + method.__doc__ = doccer.docformat(method.__doc__, wishart_docdict_params) + +_multinomial_doc_default_callparams = """\ +n : int + Number of trials +p : array_like + Probability of a trial falling into each category; should sum to 1 +""" + +_multinomial_doc_callparams_note = """\ +`n` should be a nonnegative integer. Each element of `p` should be in the +interval :math:`[0,1]` and the elements should sum to 1. If they do not sum to +1, the last element of the `p` array is not used and is replaced with the +remaining probability left over from the earlier elements. +""" + +_multinomial_doc_frozen_callparams = "" + +_multinomial_doc_frozen_callparams_note = """\ +See class definition for a detailed description of parameters.""" + +multinomial_docdict_params = { + '_doc_default_callparams': _multinomial_doc_default_callparams, + '_doc_callparams_note': _multinomial_doc_callparams_note, + '_doc_random_state': _doc_random_state +} + +multinomial_docdict_noparams = { + '_doc_default_callparams': _multinomial_doc_frozen_callparams, + '_doc_callparams_note': _multinomial_doc_frozen_callparams_note, + '_doc_random_state': _doc_random_state +} + + +class multinomial_gen(multi_rv_generic): + r"""A multinomial random variable. + + Methods + ------- + pmf(x, n, p) + Probability mass function. + logpmf(x, n, p) + Log of the probability mass function. + rvs(n, p, size=1, random_state=None) + Draw random samples from a multinomial distribution. + entropy(n, p) + Compute the entropy of the multinomial distribution. + cov(n, p) + Compute the covariance matrix of the multinomial distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + %(_doc_random_state)s + + Notes + ----- + %(_doc_callparams_note)s + + The probability mass function for `multinomial` is + + .. math:: + + f(x) = \frac{n!}{x_1! \cdots x_k!} p_1^{x_1} \cdots p_k^{x_k}, + + supported on :math:`x=(x_1, \ldots, x_k)` where each :math:`x_i` is a + nonnegative integer and their sum is :math:`n`. + + .. versionadded:: 0.19.0 + + Examples + -------- + + >>> from scipy.stats import multinomial + >>> rv = multinomial(8, [0.3, 0.2, 0.5]) + >>> rv.pmf([1, 3, 4]) + 0.042000000000000072 + + The multinomial distribution for :math:`k=2` is identical to the + corresponding binomial distribution (tiny numerical differences + notwithstanding): + + >>> from scipy.stats import binom + >>> multinomial.pmf([3, 4], n=7, p=[0.4, 0.6]) + 0.29030399999999973 + >>> binom.pmf(3, 7, 0.4) + 0.29030400000000012 + + The functions ``pmf``, ``logpmf``, ``entropy``, and ``cov`` support + broadcasting, under the convention that the vector parameters (``x`` and + ``p``) are interpreted as if each row along the last axis is a single + object. For instance: + + >>> multinomial.pmf([[3, 4], [3, 5]], n=[7, 8], p=[.3, .7]) + array([0.2268945, 0.25412184]) + + Here, ``x.shape == (2, 2)``, ``n.shape == (2,)``, and ``p.shape == (2,)``, + but following the rules mentioned above they behave as if the rows + ``[3, 4]`` and ``[3, 5]`` in ``x`` and ``[.3, .7]`` in ``p`` were a single + object, and as if we had ``x.shape = (2,)``, ``n.shape = (2,)``, and + ``p.shape = ()``. To obtain the individual elements without broadcasting, + we would do this: + + >>> multinomial.pmf([3, 4], n=7, p=[.3, .7]) + 0.2268945 + >>> multinomial.pmf([3, 5], 8, p=[.3, .7]) + 0.25412184 + + This broadcasting also works for ``cov``, where the output objects are + square matrices of size ``p.shape[-1]``. For example: + + >>> multinomial.cov([4, 5], [[.3, .7], [.4, .6]]) + array([[[ 0.84, -0.84], + [-0.84, 0.84]], + [[ 1.2 , -1.2 ], + [-1.2 , 1.2 ]]]) + + In this example, ``n.shape == (2,)`` and ``p.shape == (2, 2)``, and + following the rules above, these broadcast as if ``p.shape == (2,)``. + Thus the result should also be of shape ``(2,)``, but since each output is + a :math:`2 \times 2` matrix, the result in fact has shape ``(2, 2, 2)``, + where ``result[0]`` is equal to ``multinomial.cov(n=4, p=[.3, .7])`` and + ``result[1]`` is equal to ``multinomial.cov(n=5, p=[.4, .6])``. + + Alternatively, the object may be called (as a function) to fix the `n` and + `p` parameters, returning a "frozen" multinomial random variable: + + >>> rv = multinomial(n=7, p=[.3, .7]) + >>> # Frozen object with the same methods but holding the given + >>> # degrees of freedom and scale fixed. + + See also + -------- + scipy.stats.binom : The binomial distribution. + numpy.random.Generator.multinomial : Sampling from the multinomial distribution. + scipy.stats.multivariate_hypergeom : + The multivariate hypergeometric distribution. + """ + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = \ + doccer.docformat(self.__doc__, multinomial_docdict_params) + + def __call__(self, n, p, seed=None): + """Create a frozen multinomial distribution. + + See `multinomial_frozen` for more information. + """ + return multinomial_frozen(n, p, seed) + + def _process_parameters(self, n, p, eps=1e-15): + """Returns: n_, p_, npcond. + + n_ and p_ are arrays of the correct shape; npcond is a boolean array + flagging values out of the domain. + """ + p = np.array(p, dtype=np.float64, copy=True) + p_adjusted = 1. - p[..., :-1].sum(axis=-1) + i_adjusted = np.abs(p_adjusted) > eps + p[i_adjusted, -1] = p_adjusted[i_adjusted] + + # true for bad p + pcond = np.any(p < 0, axis=-1) + pcond |= np.any(p > 1, axis=-1) + + n = np.array(n, dtype=int, copy=True) + + # true for bad n + ncond = n < 0 + + return n, p, ncond | pcond + + def _process_quantiles(self, x, n, p): + """Returns: x_, xcond. + + x_ is an int array; xcond is a boolean array flagging values out of the + domain. + """ + xx = np.asarray(x, dtype=int) + + if xx.ndim == 0: + raise ValueError("x must be an array.") + + if xx.size != 0 and not xx.shape[-1] == p.shape[-1]: + raise ValueError("Size of each quantile should be size of p: " + "received %d, but expected %d." % + (xx.shape[-1], p.shape[-1])) + + # true for x out of the domain + cond = np.any(xx != x, axis=-1) + cond |= np.any(xx < 0, axis=-1) + cond = cond | (np.sum(xx, axis=-1) != n) + + return xx, cond + + def _checkresult(self, result, cond, bad_value): + result = np.asarray(result) + + if cond.ndim != 0: + result[cond] = bad_value + elif cond: + if result.ndim == 0: + return bad_value + result[...] = bad_value + return result + + def _logpmf(self, x, n, p): + return gammaln(n+1) + np.sum(xlogy(x, p) - gammaln(x+1), axis=-1) + + def logpmf(self, x, n, p): + """Log of the Multinomial probability mass function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + %(_doc_default_callparams)s + + Returns + ------- + logpmf : ndarray or scalar + Log of the probability mass function evaluated at `x` + + Notes + ----- + %(_doc_callparams_note)s + """ + n, p, npcond = self._process_parameters(n, p) + x, xcond = self._process_quantiles(x, n, p) + + result = self._logpmf(x, n, p) + + # replace values for which x was out of the domain; broadcast + # xcond to the right shape + xcond_ = xcond | np.zeros(npcond.shape, dtype=np.bool_) + result = self._checkresult(result, xcond_, -np.inf) + + # replace values bad for n or p; broadcast npcond to the right shape + npcond_ = npcond | np.zeros(xcond.shape, dtype=np.bool_) + return self._checkresult(result, npcond_, np.nan) + + def pmf(self, x, n, p): + """Multinomial probability mass function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + %(_doc_default_callparams)s + + Returns + ------- + pmf : ndarray or scalar + Probability density function evaluated at `x` + + Notes + ----- + %(_doc_callparams_note)s + """ + return np.exp(self.logpmf(x, n, p)) + + def mean(self, n, p): + """Mean of the Multinomial distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + mean : float + The mean of the distribution + """ + n, p, npcond = self._process_parameters(n, p) + result = n[..., np.newaxis]*p + return self._checkresult(result, npcond, np.nan) + + def cov(self, n, p): + """Covariance matrix of the multinomial distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + cov : ndarray + The covariance matrix of the distribution + """ + n, p, npcond = self._process_parameters(n, p) + + nn = n[..., np.newaxis, np.newaxis] + result = nn * np.einsum('...j,...k->...jk', -p, p) + + # change the diagonal + for i in range(p.shape[-1]): + result[..., i, i] += n*p[..., i] + + return self._checkresult(result, npcond, np.nan) + + def entropy(self, n, p): + r"""Compute the entropy of the multinomial distribution. + + The entropy is computed using this expression: + + .. math:: + + f(x) = - \log n! - n\sum_{i=1}^k p_i \log p_i + + \sum_{i=1}^k \sum_{x=0}^n \binom n x p_i^x(1-p_i)^{n-x} \log x! + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + h : scalar + Entropy of the Multinomial distribution + + Notes + ----- + %(_doc_callparams_note)s + """ + n, p, npcond = self._process_parameters(n, p) + + x = np.r_[1:np.max(n)+1] + + term1 = n*np.sum(entr(p), axis=-1) + term1 -= gammaln(n+1) + + n = n[..., np.newaxis] + new_axes_needed = max(p.ndim, n.ndim) - x.ndim + 1 + x.shape += (1,)*new_axes_needed + + term2 = np.sum(binom.pmf(x, n, p)*gammaln(x+1), + axis=(-1, -1-new_axes_needed)) + + return self._checkresult(term1 + term2, npcond, np.nan) + + def rvs(self, n, p, size=None, random_state=None): + """Draw random samples from a Multinomial distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + size : integer or iterable of integers, optional + Number of samples to draw (default 1). + %(_doc_random_state)s + + Returns + ------- + rvs : ndarray or scalar + Random variates of shape (`size`, `len(p)`) + + Notes + ----- + %(_doc_callparams_note)s + """ + n, p, npcond = self._process_parameters(n, p) + random_state = self._get_random_state(random_state) + return random_state.multinomial(n, p, size) + + +multinomial = multinomial_gen() + + +class multinomial_frozen(multi_rv_frozen): + r"""Create a frozen Multinomial distribution. + + Parameters + ---------- + n : int + number of trials + p: array_like + probability of a trial falling into each category; should sum to 1 + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance then + that instance is used. + """ + def __init__(self, n, p, seed=None): + self._dist = multinomial_gen(seed) + self.n, self.p, self.npcond = self._dist._process_parameters(n, p) + + # monkey patch self._dist + def _process_parameters(n, p): + return self.n, self.p, self.npcond + + self._dist._process_parameters = _process_parameters + + def logpmf(self, x): + return self._dist.logpmf(x, self.n, self.p) + + def pmf(self, x): + return self._dist.pmf(x, self.n, self.p) + + def mean(self): + return self._dist.mean(self.n, self.p) + + def cov(self): + return self._dist.cov(self.n, self.p) + + def entropy(self): + return self._dist.entropy(self.n, self.p) + + def rvs(self, size=1, random_state=None): + return self._dist.rvs(self.n, self.p, size, random_state) + + +# Set frozen generator docstrings from corresponding docstrings in +# multinomial and fill in default strings in class docstrings +for name in ['logpmf', 'pmf', 'mean', 'cov', 'rvs']: + method = multinomial_gen.__dict__[name] + method_frozen = multinomial_frozen.__dict__[name] + method_frozen.__doc__ = doccer.docformat( + method.__doc__, multinomial_docdict_noparams) + method.__doc__ = doccer.docformat(method.__doc__, + multinomial_docdict_params) + + +class special_ortho_group_gen(multi_rv_generic): + r"""A Special Orthogonal matrix (SO(N)) random variable. + + Return a random rotation matrix, drawn from the Haar distribution + (the only uniform distribution on SO(N)) with a determinant of +1. + + The `dim` keyword specifies the dimension N. + + Methods + ------- + rvs(dim=None, size=1, random_state=None) + Draw random samples from SO(N). + + Parameters + ---------- + dim : scalar + Dimension of matrices + seed : {None, int, np.random.RandomState, np.random.Generator}, optional + Used for drawing random variates. + If `seed` is `None`, the `~np.random.RandomState` singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, seeded + with seed. + If `seed` is already a ``RandomState`` or ``Generator`` instance, + then that object is used. + Default is `None`. + + Notes + ----- + This class is wrapping the random_rot code from the MDP Toolkit, + https://github.com/mdp-toolkit/mdp-toolkit + + Return a random rotation matrix, drawn from the Haar distribution + (the only uniform distribution on SO(N)). + The algorithm is described in the paper + Stewart, G.W., "The efficient generation of random orthogonal + matrices with an application to condition estimators", SIAM Journal + on Numerical Analysis, 17(3), pp. 403-409, 1980. + For more information see + https://en.wikipedia.org/wiki/Orthogonal_matrix#Randomization + + See also the similar `ortho_group`. For a random rotation in three + dimensions, see `scipy.spatial.transform.Rotation.random`. + + Examples + -------- + >>> import numpy as np + >>> from scipy.stats import special_ortho_group + >>> x = special_ortho_group.rvs(3) + + >>> np.dot(x, x.T) + array([[ 1.00000000e+00, 1.13231364e-17, -2.86852790e-16], + [ 1.13231364e-17, 1.00000000e+00, -1.46845020e-16], + [ -2.86852790e-16, -1.46845020e-16, 1.00000000e+00]]) + + >>> import scipy.linalg + >>> scipy.linalg.det(x) + 1.0 + + This generates one random matrix from SO(3). It is orthogonal and + has a determinant of 1. + + Alternatively, the object may be called (as a function) to fix the `dim` + parameter, returning a "frozen" special_ortho_group random variable: + + >>> rv = special_ortho_group(5) + >>> # Frozen object with the same methods but holding the + >>> # dimension parameter fixed. + + See Also + -------- + ortho_group, scipy.spatial.transform.Rotation.random + + """ + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__) + + def __call__(self, dim=None, seed=None): + """Create a frozen SO(N) distribution. + + See `special_ortho_group_frozen` for more information. + """ + return special_ortho_group_frozen(dim, seed=seed) + + def _process_parameters(self, dim): + """Dimension N must be specified; it cannot be inferred.""" + if dim is None or not np.isscalar(dim) or dim <= 1 or dim != int(dim): + raise ValueError("""Dimension of rotation must be specified, + and must be a scalar greater than 1.""") + + return dim + + def rvs(self, dim, size=1, random_state=None): + """Draw random samples from SO(N). + + Parameters + ---------- + dim : integer + Dimension of rotation space (N). + size : integer, optional + Number of samples to draw (default 1). + + Returns + ------- + rvs : ndarray or scalar + Random size N-dimensional matrices, dimension (size, dim, dim) + + """ + random_state = self._get_random_state(random_state) + + size = int(size) + size = (size,) if size > 1 else () + + dim = self._process_parameters(dim) + + # H represents a (dim, dim) matrix, while D represents the diagonal of + # a (dim, dim) diagonal matrix. The algorithm that follows is + # broadcasted on the leading shape in `size` to vectorize along + # samples. + H = np.empty(size + (dim, dim)) + H[..., :, :] = np.eye(dim) + D = np.empty(size + (dim,)) + + for n in range(dim-1): + + # x is a vector with length dim-n, xrow and xcol are views of it as + # a row vector and column vector respectively. It's important they + # are views and not copies because we are going to modify x + # in-place. + x = random_state.normal(size=size + (dim-n,)) + xrow = x[..., None, :] + xcol = x[..., :, None] + + # This is the squared norm of x, without vectorization it would be + # dot(x, x), to have proper broadcasting we use matmul and squeeze + # out (convert to scalar) the resulting 1x1 matrix + norm2 = np.matmul(xrow, xcol).squeeze((-2, -1)) + + x0 = x[..., 0].copy() + D[..., n] = np.where(x0 != 0, np.sign(x0), 1) + x[..., 0] += D[..., n]*np.sqrt(norm2) + + # In renormalizing x we have to append an additional axis with + # [..., None] to broadcast the scalar against the vector x + x /= np.sqrt((norm2 - x0**2 + x[..., 0]**2) / 2.)[..., None] + + # Householder transformation, without vectorization the RHS can be + # written as outer(H @ x, x) (apart from the slicing) + H[..., :, n:] -= np.matmul(H[..., :, n:], xcol) * xrow + + D[..., -1] = (-1)**(dim-1)*D[..., :-1].prod(axis=-1) + + # Without vectorization this could be written as H = diag(D) @ H, + # left-multiplication by a diagonal matrix amounts to multiplying each + # row of H by an element of the diagonal, so we add a dummy axis for + # the column index + H *= D[..., :, None] + return H + + +special_ortho_group = special_ortho_group_gen() + + +class special_ortho_group_frozen(multi_rv_frozen): + def __init__(self, dim=None, seed=None): + """Create a frozen SO(N) distribution. + + Parameters + ---------- + dim : scalar + Dimension of matrices + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + + Examples + -------- + >>> from scipy.stats import special_ortho_group + >>> g = special_ortho_group(5) + >>> x = g.rvs() + + """ # numpy/numpydoc#87 # noqa: E501 + self._dist = special_ortho_group_gen(seed) + self.dim = self._dist._process_parameters(dim) + + def rvs(self, size=1, random_state=None): + return self._dist.rvs(self.dim, size, random_state) + + +class ortho_group_gen(multi_rv_generic): + r"""An Orthogonal matrix (O(N)) random variable. + + Return a random orthogonal matrix, drawn from the O(N) Haar + distribution (the only uniform distribution on O(N)). + + The `dim` keyword specifies the dimension N. + + Methods + ------- + rvs(dim=None, size=1, random_state=None) + Draw random samples from O(N). + + Parameters + ---------- + dim : scalar + Dimension of matrices + seed : {None, int, np.random.RandomState, np.random.Generator}, optional + Used for drawing random variates. + If `seed` is `None`, the `~np.random.RandomState` singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, seeded + with seed. + If `seed` is already a ``RandomState`` or ``Generator`` instance, + then that object is used. + Default is `None`. + + Notes + ----- + This class is closely related to `special_ortho_group`. + + Some care is taken to avoid numerical error, as per the paper by Mezzadri. + + References + ---------- + .. [1] F. Mezzadri, "How to generate random matrices from the classical + compact groups", :arXiv:`math-ph/0609050v2`. + + Examples + -------- + >>> import numpy as np + >>> from scipy.stats import ortho_group + >>> x = ortho_group.rvs(3) + + >>> np.dot(x, x.T) + array([[ 1.00000000e+00, 1.13231364e-17, -2.86852790e-16], + [ 1.13231364e-17, 1.00000000e+00, -1.46845020e-16], + [ -2.86852790e-16, -1.46845020e-16, 1.00000000e+00]]) + + >>> import scipy.linalg + >>> np.fabs(scipy.linalg.det(x)) + 1.0 + + This generates one random matrix from O(3). It is orthogonal and + has a determinant of +1 or -1. + + Alternatively, the object may be called (as a function) to fix the `dim` + parameter, returning a "frozen" ortho_group random variable: + + >>> rv = ortho_group(5) + >>> # Frozen object with the same methods but holding the + >>> # dimension parameter fixed. + + See Also + -------- + special_ortho_group + """ + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__) + + def __call__(self, dim=None, seed=None): + """Create a frozen O(N) distribution. + + See `ortho_group_frozen` for more information. + """ + return ortho_group_frozen(dim, seed=seed) + + def _process_parameters(self, dim): + """Dimension N must be specified; it cannot be inferred.""" + if dim is None or not np.isscalar(dim) or dim <= 1 or dim != int(dim): + raise ValueError("Dimension of rotation must be specified," + "and must be a scalar greater than 1.") + + return dim + + def rvs(self, dim, size=1, random_state=None): + """Draw random samples from O(N). + + Parameters + ---------- + dim : integer + Dimension of rotation space (N). + size : integer, optional + Number of samples to draw (default 1). + + Returns + ------- + rvs : ndarray or scalar + Random size N-dimensional matrices, dimension (size, dim, dim) + + """ + random_state = self._get_random_state(random_state) + + size = int(size) + + dim = self._process_parameters(dim) + + size = (size,) if size > 1 else () + z = random_state.normal(size=size + (dim, dim)) + q, r = np.linalg.qr(z) + # The last two dimensions are the rows and columns of R matrices. + # Extract the diagonals. Note that this eliminates a dimension. + d = r.diagonal(offset=0, axis1=-2, axis2=-1) + # Add back a dimension for proper broadcasting: we're dividing + # each row of each R matrix by the diagonal of the R matrix. + q *= (d/abs(d))[..., np.newaxis, :] # to broadcast properly + return q + + +ortho_group = ortho_group_gen() + + +class ortho_group_frozen(multi_rv_frozen): + def __init__(self, dim=None, seed=None): + """Create a frozen O(N) distribution. + + Parameters + ---------- + dim : scalar + Dimension of matrices + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + + Examples + -------- + >>> from scipy.stats import ortho_group + >>> g = ortho_group(5) + >>> x = g.rvs() + + """ # numpy/numpydoc#87 # noqa: E501 + self._dist = ortho_group_gen(seed) + self.dim = self._dist._process_parameters(dim) + + def rvs(self, size=1, random_state=None): + return self._dist.rvs(self.dim, size, random_state) + + +class random_correlation_gen(multi_rv_generic): + r"""A random correlation matrix. + + Return a random correlation matrix, given a vector of eigenvalues. + + The `eigs` keyword specifies the eigenvalues of the correlation matrix, + and implies the dimension. + + Methods + ------- + rvs(eigs=None, random_state=None) + Draw random correlation matrices, all with eigenvalues eigs. + + Parameters + ---------- + eigs : 1d ndarray + Eigenvalues of correlation matrix + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + tol : float, optional + Tolerance for input parameter checks + diag_tol : float, optional + Tolerance for deviation of the diagonal of the resulting + matrix. Default: 1e-7 + + Raises + ------ + RuntimeError + Floating point error prevented generating a valid correlation + matrix. + + Returns + ------- + rvs : ndarray or scalar + Random size N-dimensional matrices, dimension (size, dim, dim), + each having eigenvalues eigs. + + Notes + ----- + + Generates a random correlation matrix following a numerically stable + algorithm spelled out by Davies & Higham. This algorithm uses a single O(N) + similarity transformation to construct a symmetric positive semi-definite + matrix, and applies a series of Givens rotations to scale it to have ones + on the diagonal. + + References + ---------- + + .. [1] Davies, Philip I; Higham, Nicholas J; "Numerically stable generation + of correlation matrices and their factors", BIT 2000, Vol. 40, + No. 4, pp. 640 651 + + Examples + -------- + >>> import numpy as np + >>> from scipy.stats import random_correlation + >>> rng = np.random.default_rng() + >>> x = random_correlation.rvs((.5, .8, 1.2, 1.5), random_state=rng) + >>> x + array([[ 1. , -0.02423399, 0.03130519, 0.4946965 ], + [-0.02423399, 1. , 0.20334736, 0.04039817], + [ 0.03130519, 0.20334736, 1. , 0.02694275], + [ 0.4946965 , 0.04039817, 0.02694275, 1. ]]) + >>> import scipy.linalg + >>> e, v = scipy.linalg.eigh(x) + >>> e + array([ 0.5, 0.8, 1.2, 1.5]) + + """ + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__) + + def __call__(self, eigs, seed=None, tol=1e-13, diag_tol=1e-7): + """Create a frozen random correlation matrix. + + See `random_correlation_frozen` for more information. + """ + return random_correlation_frozen(eigs, seed=seed, tol=tol, + diag_tol=diag_tol) + + def _process_parameters(self, eigs, tol): + eigs = np.asarray(eigs, dtype=float) + dim = eigs.size + + if eigs.ndim != 1 or eigs.shape[0] != dim or dim <= 1: + raise ValueError("Array 'eigs' must be a vector of length " + "greater than 1.") + + if np.fabs(np.sum(eigs) - dim) > tol: + raise ValueError("Sum of eigenvalues must equal dimensionality.") + + for x in eigs: + if x < -tol: + raise ValueError("All eigenvalues must be non-negative.") + + return dim, eigs + + def _givens_to_1(self, aii, ajj, aij): + """Computes a 2x2 Givens matrix to put 1's on the diagonal. + + The input matrix is a 2x2 symmetric matrix M = [ aii aij ; aij ajj ]. + + The output matrix g is a 2x2 anti-symmetric matrix of the form + [ c s ; -s c ]; the elements c and s are returned. + + Applying the output matrix to the input matrix (as b=g.T M g) + results in a matrix with bii=1, provided tr(M) - det(M) >= 1 + and floating point issues do not occur. Otherwise, some other + valid rotation is returned. When tr(M)==2, also bjj=1. + + """ + aiid = aii - 1. + ajjd = ajj - 1. + + if ajjd == 0: + # ajj==1, so swap aii and ajj to avoid division by zero + return 0., 1. + + dd = math.sqrt(max(aij**2 - aiid*ajjd, 0)) + + # The choice of t should be chosen to avoid cancellation [1] + t = (aij + math.copysign(dd, aij)) / ajjd + c = 1. / math.sqrt(1. + t*t) + if c == 0: + # Underflow + s = 1.0 + else: + s = c*t + return c, s + + def _to_corr(self, m): + """ + Given a psd matrix m, rotate to put one's on the diagonal, turning it + into a correlation matrix. This also requires the trace equal the + dimensionality. Note: modifies input matrix + """ + # Check requirements for in-place Givens + if not (m.flags.c_contiguous and m.dtype == np.float64 and + m.shape[0] == m.shape[1]): + raise ValueError() + + d = m.shape[0] + for i in range(d-1): + if m[i, i] == 1: + continue + elif m[i, i] > 1: + for j in range(i+1, d): + if m[j, j] < 1: + break + else: + for j in range(i+1, d): + if m[j, j] > 1: + break + + c, s = self._givens_to_1(m[i, i], m[j, j], m[i, j]) + + # Use BLAS to apply Givens rotations in-place. Equivalent to: + # g = np.eye(d) + # g[i, i] = g[j,j] = c + # g[j, i] = -s; g[i, j] = s + # m = np.dot(g.T, np.dot(m, g)) + mv = m.ravel() + drot(mv, mv, c, -s, n=d, + offx=i*d, incx=1, offy=j*d, incy=1, + overwrite_x=True, overwrite_y=True) + drot(mv, mv, c, -s, n=d, + offx=i, incx=d, offy=j, incy=d, + overwrite_x=True, overwrite_y=True) + + return m + + def rvs(self, eigs, random_state=None, tol=1e-13, diag_tol=1e-7): + """Draw random correlation matrices. + + Parameters + ---------- + eigs : 1d ndarray + Eigenvalues of correlation matrix + tol : float, optional + Tolerance for input parameter checks + diag_tol : float, optional + Tolerance for deviation of the diagonal of the resulting + matrix. Default: 1e-7 + + Raises + ------ + RuntimeError + Floating point error prevented generating a valid correlation + matrix. + + Returns + ------- + rvs : ndarray or scalar + Random size N-dimensional matrices, dimension (size, dim, dim), + each having eigenvalues eigs. + + """ + dim, eigs = self._process_parameters(eigs, tol=tol) + + random_state = self._get_random_state(random_state) + + m = ortho_group.rvs(dim, random_state=random_state) + m = np.dot(np.dot(m, np.diag(eigs)), m.T) # Set the trace of m + m = self._to_corr(m) # Carefully rotate to unit diagonal + + # Check diagonal + if abs(m.diagonal() - 1).max() > diag_tol: + raise RuntimeError("Failed to generate a valid correlation matrix") + + return m + + +random_correlation = random_correlation_gen() + + +class random_correlation_frozen(multi_rv_frozen): + def __init__(self, eigs, seed=None, tol=1e-13, diag_tol=1e-7): + """Create a frozen random correlation matrix distribution. + + Parameters + ---------- + eigs : 1d ndarray + Eigenvalues of correlation matrix + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + tol : float, optional + Tolerance for input parameter checks + diag_tol : float, optional + Tolerance for deviation of the diagonal of the resulting + matrix. Default: 1e-7 + + Raises + ------ + RuntimeError + Floating point error prevented generating a valid correlation + matrix. + + Returns + ------- + rvs : ndarray or scalar + Random size N-dimensional matrices, dimension (size, dim, dim), + each having eigenvalues eigs. + """ # numpy/numpydoc#87 # noqa: E501 + + self._dist = random_correlation_gen(seed) + self.tol = tol + self.diag_tol = diag_tol + _, self.eigs = self._dist._process_parameters(eigs, tol=self.tol) + + def rvs(self, random_state=None): + return self._dist.rvs(self.eigs, random_state=random_state, + tol=self.tol, diag_tol=self.diag_tol) + + +class unitary_group_gen(multi_rv_generic): + r"""A matrix-valued U(N) random variable. + + Return a random unitary matrix. + + The `dim` keyword specifies the dimension N. + + Methods + ------- + rvs(dim=None, size=1, random_state=None) + Draw random samples from U(N). + + Parameters + ---------- + dim : scalar + Dimension of matrices, must be greater than 1. + seed : {None, int, np.random.RandomState, np.random.Generator}, optional + Used for drawing random variates. + If `seed` is `None`, the `~np.random.RandomState` singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, seeded + with seed. + If `seed` is already a ``RandomState`` or ``Generator`` instance, + then that object is used. + Default is `None`. + + Notes + ----- + This class is similar to `ortho_group`. + + References + ---------- + .. [1] F. Mezzadri, "How to generate random matrices from the classical + compact groups", :arXiv:`math-ph/0609050v2`. + + Examples + -------- + >>> import numpy as np + >>> from scipy.stats import unitary_group + >>> x = unitary_group.rvs(3) + + >>> np.dot(x, x.conj().T) + array([[ 1.00000000e+00, 1.13231364e-17, -2.86852790e-16], + [ 1.13231364e-17, 1.00000000e+00, -1.46845020e-16], + [ -2.86852790e-16, -1.46845020e-16, 1.00000000e+00]]) + + This generates one random matrix from U(3). The dot product confirms that + it is unitary up to machine precision. + + Alternatively, the object may be called (as a function) to fix the `dim` + parameter, return a "frozen" unitary_group random variable: + + >>> rv = unitary_group(5) + + See Also + -------- + ortho_group + + """ + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__) + + def __call__(self, dim=None, seed=None): + """Create a frozen (U(N)) n-dimensional unitary matrix distribution. + + See `unitary_group_frozen` for more information. + """ + return unitary_group_frozen(dim, seed=seed) + + def _process_parameters(self, dim): + """Dimension N must be specified; it cannot be inferred.""" + if dim is None or not np.isscalar(dim) or dim <= 1 or dim != int(dim): + raise ValueError("Dimension of rotation must be specified," + "and must be a scalar greater than 1.") + + return dim + + def rvs(self, dim, size=1, random_state=None): + """Draw random samples from U(N). + + Parameters + ---------- + dim : integer + Dimension of space (N). + size : integer, optional + Number of samples to draw (default 1). + + Returns + ------- + rvs : ndarray or scalar + Random size N-dimensional matrices, dimension (size, dim, dim) + + """ + random_state = self._get_random_state(random_state) + + size = int(size) + + dim = self._process_parameters(dim) + + size = (size,) if size > 1 else () + z = 1/math.sqrt(2)*(random_state.normal(size=size + (dim, dim)) + + 1j*random_state.normal(size=size + (dim, dim))) + q, r = np.linalg.qr(z) + # The last two dimensions are the rows and columns of R matrices. + # Extract the diagonals. Note that this eliminates a dimension. + d = r.diagonal(offset=0, axis1=-2, axis2=-1) + # Add back a dimension for proper broadcasting: we're dividing + # each row of each R matrix by the diagonal of the R matrix. + q *= (d/abs(d))[..., np.newaxis, :] # to broadcast properly + return q + + +unitary_group = unitary_group_gen() + + +class unitary_group_frozen(multi_rv_frozen): + def __init__(self, dim=None, seed=None): + """Create a frozen (U(N)) n-dimensional unitary matrix distribution. + + Parameters + ---------- + dim : scalar + Dimension of matrices + seed : {None, int, `numpy.random.Generator`, `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + + Examples + -------- + >>> from scipy.stats import unitary_group + >>> x = unitary_group(3) + >>> x.rvs() + + """ # numpy/numpydoc#87 # noqa: E501 + self._dist = unitary_group_gen(seed) + self.dim = self._dist._process_parameters(dim) + + def rvs(self, size=1, random_state=None): + return self._dist.rvs(self.dim, size, random_state) + + +_mvt_doc_default_callparams = """\ +loc : array_like, optional + Location of the distribution. (default ``0``) +shape : array_like, optional + Positive semidefinite matrix of the distribution. (default ``1``) +df : float, optional + Degrees of freedom of the distribution; must be greater than zero. + If ``np.inf`` then results are multivariate normal. The default is ``1``. +allow_singular : bool, optional + Whether to allow a singular matrix. (default ``False``) +""" + +_mvt_doc_callparams_note = """\ +Setting the parameter `loc` to ``None`` is equivalent to having `loc` +be the zero-vector. The parameter `shape` can be a scalar, in which case +the shape matrix is the identity times that value, a vector of +diagonal entries for the shape matrix, or a two-dimensional array_like. +""" + +_mvt_doc_frozen_callparams_note = """\ +See class definition for a detailed description of parameters.""" + +mvt_docdict_params = { + '_mvt_doc_default_callparams': _mvt_doc_default_callparams, + '_mvt_doc_callparams_note': _mvt_doc_callparams_note, + '_doc_random_state': _doc_random_state +} + +mvt_docdict_noparams = { + '_mvt_doc_default_callparams': "", + '_mvt_doc_callparams_note': _mvt_doc_frozen_callparams_note, + '_doc_random_state': _doc_random_state +} + + +class multivariate_t_gen(multi_rv_generic): + r"""A multivariate t-distributed random variable. + + The `loc` parameter specifies the location. The `shape` parameter specifies + the positive semidefinite shape matrix. The `df` parameter specifies the + degrees of freedom. + + In addition to calling the methods below, the object itself may be called + as a function to fix the location, shape matrix, and degrees of freedom + parameters, returning a "frozen" multivariate t-distribution random. + + Methods + ------- + pdf(x, loc=None, shape=1, df=1, allow_singular=False) + Probability density function. + logpdf(x, loc=None, shape=1, df=1, allow_singular=False) + Log of the probability density function. + cdf(x, loc=None, shape=1, df=1, allow_singular=False, *, + maxpts=None, lower_limit=None, random_state=None) + Cumulative distribution function. + rvs(loc=None, shape=1, df=1, size=1, random_state=None) + Draw random samples from a multivariate t-distribution. + entropy(loc=None, shape=1, df=1) + Differential entropy of a multivariate t-distribution. + + Parameters + ---------- + %(_mvt_doc_default_callparams)s + %(_doc_random_state)s + + Notes + ----- + %(_mvt_doc_callparams_note)s + The matrix `shape` must be a (symmetric) positive semidefinite matrix. The + determinant and inverse of `shape` are computed as the pseudo-determinant + and pseudo-inverse, respectively, so that `shape` does not need to have + full rank. + + The probability density function for `multivariate_t` is + + .. math:: + + f(x) = \frac{\Gamma((\nu + p)/2)}{\Gamma(\nu/2)\nu^{p/2}\pi^{p/2}|\Sigma|^{1/2}} + \left[1 + \frac{1}{\nu} (\mathbf{x} - \boldsymbol{\mu})^{\top} + \boldsymbol{\Sigma}^{-1} + (\mathbf{x} - \boldsymbol{\mu}) \right]^{-(\nu + p)/2}, + + where :math:`p` is the dimension of :math:`\mathbf{x}`, + :math:`\boldsymbol{\mu}` is the :math:`p`-dimensional location, + :math:`\boldsymbol{\Sigma}` the :math:`p \times p`-dimensional shape + matrix, and :math:`\nu` is the degrees of freedom. + + .. versionadded:: 1.6.0 + + References + ---------- + .. [1] Arellano-Valle et al. "Shannon Entropy and Mutual Information for + Multivariate Skew-Elliptical Distributions". Scandinavian Journal + of Statistics. Vol. 40, issue 1. + + Examples + -------- + The object may be called (as a function) to fix the `loc`, `shape`, + `df`, and `allow_singular` parameters, returning a "frozen" + multivariate_t random variable: + + >>> import numpy as np + >>> from scipy.stats import multivariate_t + >>> rv = multivariate_t([1.0, -0.5], [[2.1, 0.3], [0.3, 1.5]], df=2) + >>> # Frozen object with the same methods but holding the given location, + >>> # scale, and degrees of freedom fixed. + + Create a contour plot of the PDF. + + >>> import matplotlib.pyplot as plt + >>> x, y = np.mgrid[-1:3:.01, -2:1.5:.01] + >>> pos = np.dstack((x, y)) + >>> fig, ax = plt.subplots(1, 1) + >>> ax.set_aspect('equal') + >>> plt.contourf(x, y, rv.pdf(pos)) + + """ + + def __init__(self, seed=None): + """Initialize a multivariate t-distributed random variable. + + Parameters + ---------- + seed : Random state. + + """ + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__, mvt_docdict_params) + self._random_state = check_random_state(seed) + + def __call__(self, loc=None, shape=1, df=1, allow_singular=False, + seed=None): + """Create a frozen multivariate t-distribution. + + See `multivariate_t_frozen` for parameters. + """ + if df == np.inf: + return multivariate_normal_frozen(mean=loc, cov=shape, + allow_singular=allow_singular, + seed=seed) + return multivariate_t_frozen(loc=loc, shape=shape, df=df, + allow_singular=allow_singular, seed=seed) + + def pdf(self, x, loc=None, shape=1, df=1, allow_singular=False): + """Multivariate t-distribution probability density function. + + Parameters + ---------- + x : array_like + Points at which to evaluate the probability density function. + %(_mvt_doc_default_callparams)s + + Returns + ------- + pdf : Probability density function evaluated at `x`. + + Examples + -------- + >>> from scipy.stats import multivariate_t + >>> x = [0.4, 5] + >>> loc = [0, 1] + >>> shape = [[1, 0.1], [0.1, 1]] + >>> df = 7 + >>> multivariate_t.pdf(x, loc, shape, df) + 0.00075713 + + """ + dim, loc, shape, df = self._process_parameters(loc, shape, df) + x = self._process_quantiles(x, dim) + shape_info = _PSD(shape, allow_singular=allow_singular) + logpdf = self._logpdf(x, loc, shape_info.U, shape_info.log_pdet, df, + dim, shape_info.rank) + return np.exp(logpdf) + + def logpdf(self, x, loc=None, shape=1, df=1): + """Log of the multivariate t-distribution probability density function. + + Parameters + ---------- + x : array_like + Points at which to evaluate the log of the probability density + function. + %(_mvt_doc_default_callparams)s + + Returns + ------- + logpdf : Log of the probability density function evaluated at `x`. + + Examples + -------- + >>> from scipy.stats import multivariate_t + >>> x = [0.4, 5] + >>> loc = [0, 1] + >>> shape = [[1, 0.1], [0.1, 1]] + >>> df = 7 + >>> multivariate_t.logpdf(x, loc, shape, df) + -7.1859802 + + See Also + -------- + pdf : Probability density function. + + """ + dim, loc, shape, df = self._process_parameters(loc, shape, df) + x = self._process_quantiles(x, dim) + shape_info = _PSD(shape) + return self._logpdf(x, loc, shape_info.U, shape_info.log_pdet, df, dim, + shape_info.rank) + + def _logpdf(self, x, loc, prec_U, log_pdet, df, dim, rank): + """Utility method `pdf`, `logpdf` for parameters. + + Parameters + ---------- + x : ndarray + Points at which to evaluate the log of the probability density + function. + loc : ndarray + Location of the distribution. + prec_U : ndarray + A decomposition such that `np.dot(prec_U, prec_U.T)` is the inverse + of the shape matrix. + log_pdet : float + Logarithm of the determinant of the shape matrix. + df : float + Degrees of freedom of the distribution. + dim : int + Dimension of the quantiles x. + rank : int + Rank of the shape matrix. + + Notes + ----- + As this function does no argument checking, it should not be called + directly; use 'logpdf' instead. + + """ + if df == np.inf: + return multivariate_normal._logpdf(x, loc, prec_U, log_pdet, rank) + + dev = x - loc + maha = np.square(np.dot(dev, prec_U)).sum(axis=-1) + + t = 0.5 * (df + dim) + A = gammaln(t) + B = gammaln(0.5 * df) + C = dim/2. * np.log(df * np.pi) + D = 0.5 * log_pdet + E = -t * np.log(1 + (1./df) * maha) + + return _squeeze_output(A - B - C - D + E) + + def _cdf(self, x, loc, shape, df, dim, maxpts=None, lower_limit=None, + random_state=None): + + # All of this - random state validation, maxpts, apply_along_axis, + # etc. needs to go in this private method unless we want + # frozen distribution's `cdf` method to duplicate it or call `cdf`, + # which would require re-processing parameters + if random_state is not None: + rng = check_random_state(random_state) + else: + rng = self._random_state + + if not maxpts: + maxpts = 1000 * dim + + x = self._process_quantiles(x, dim) + lower_limit = (np.full(loc.shape, -np.inf) + if lower_limit is None else lower_limit) + + # remove the mean + x, lower_limit = x - loc, lower_limit - loc + + b, a = np.broadcast_arrays(x, lower_limit) + i_swap = b < a + signs = (-1)**(i_swap.sum(axis=-1)) # odd # of swaps -> negative + a, b = a.copy(), b.copy() + a[i_swap], b[i_swap] = b[i_swap], a[i_swap] + n = x.shape[-1] + limits = np.concatenate((a, b), axis=-1) + + def func1d(limits): + a, b = limits[:n], limits[n:] + return _qmvt(maxpts, df, shape, a, b, rng)[0] + + res = np.apply_along_axis(func1d, -1, limits) * signs + # Fixing the output shape for existing distributions is a separate + # issue. For now, let's keep this consistent with pdf. + return _squeeze_output(res) + + def cdf(self, x, loc=None, shape=1, df=1, allow_singular=False, *, + maxpts=None, lower_limit=None, random_state=None): + """Multivariate t-distribution cumulative distribution function. + + Parameters + ---------- + x : array_like + Points at which to evaluate the cumulative distribution function. + %(_mvt_doc_default_callparams)s + maxpts : int, optional + Maximum number of points to use for integration. The default is + 1000 times the number of dimensions. + lower_limit : array_like, optional + Lower limit of integration of the cumulative distribution function. + Default is negative infinity. Must be broadcastable with `x`. + %(_doc_random_state)s + + Returns + ------- + cdf : ndarray or scalar + Cumulative distribution function evaluated at `x`. + + Examples + -------- + >>> from scipy.stats import multivariate_t + >>> x = [0.4, 5] + >>> loc = [0, 1] + >>> shape = [[1, 0.1], [0.1, 1]] + >>> df = 7 + >>> multivariate_t.cdf(x, loc, shape, df) + 0.64798491 + + """ + dim, loc, shape, df = self._process_parameters(loc, shape, df) + shape = _PSD(shape, allow_singular=allow_singular)._M + + return self._cdf(x, loc, shape, df, dim, maxpts, + lower_limit, random_state) + + def _entropy(self, dim, df=1, shape=1): + if df == np.inf: + return multivariate_normal(None, cov=shape).entropy() + + shape_info = _PSD(shape) + shape_term = 0.5 * shape_info.log_pdet + + def regular(dim, df): + halfsum = 0.5 * (dim + df) + half_df = 0.5 * df + return ( + -gammaln(halfsum) + gammaln(half_df) + + 0.5 * dim * np.log(df * np.pi) + halfsum + * (psi(halfsum) - psi(half_df)) + + shape_term + ) + + def asymptotic(dim, df): + # Formula from Wolfram Alpha: + # "asymptotic expansion -gammaln((m+d)/2) + gammaln(d/2) + (m*log(d*pi))/2 + # + ((m+d)/2) * (digamma((m+d)/2) - digamma(d/2))" + return ( + dim * norm._entropy() + dim / df + - dim * (dim - 2) * df**-2.0 / 4 + + dim**2 * (dim - 2) * df**-3.0 / 6 + + dim * (-3 * dim**3 + 8 * dim**2 - 8) * df**-4.0 / 24 + + dim**2 * (3 * dim**3 - 10 * dim**2 + 16) * df**-5.0 / 30 + + shape_term + )[()] + + # preserves ~12 digits accuracy up to at least `dim=1e5`. See gh-18465. + threshold = dim * 100 * 4 / (np.log(dim) + 1) + return _lazywhere(df >= threshold, (dim, df), f=asymptotic, f2=regular) + + def entropy(self, loc=None, shape=1, df=1): + """Calculate the differential entropy of a multivariate + t-distribution. + + Parameters + ---------- + %(_mvt_doc_default_callparams)s + + Returns + ------- + h : float + Differential entropy + + """ + dim, loc, shape, df = self._process_parameters(None, shape, df) + return self._entropy(dim, df, shape) + + def rvs(self, loc=None, shape=1, df=1, size=1, random_state=None): + """Draw random samples from a multivariate t-distribution. + + Parameters + ---------- + %(_mvt_doc_default_callparams)s + size : integer, optional + Number of samples to draw (default 1). + %(_doc_random_state)s + + Returns + ------- + rvs : ndarray or scalar + Random variates of size (`size`, `P`), where `P` is the + dimension of the random variable. + + Examples + -------- + >>> from scipy.stats import multivariate_t + >>> x = [0.4, 5] + >>> loc = [0, 1] + >>> shape = [[1, 0.1], [0.1, 1]] + >>> df = 7 + >>> multivariate_t.rvs(loc, shape, df) + array([[0.93477495, 3.00408716]]) + + """ + # For implementation details, see equation (3): + # + # Hofert, "On Sampling from the Multivariatet Distribution", 2013 + # http://rjournal.github.io/archive/2013-2/hofert.pdf + # + dim, loc, shape, df = self._process_parameters(loc, shape, df) + if random_state is not None: + rng = check_random_state(random_state) + else: + rng = self._random_state + + if np.isinf(df): + x = np.ones(size) + else: + x = rng.chisquare(df, size=size) / df + + z = rng.multivariate_normal(np.zeros(dim), shape, size=size) + samples = loc + z / np.sqrt(x)[..., None] + return _squeeze_output(samples) + + def _process_quantiles(self, x, dim): + """ + Adjust quantiles array so that last axis labels the components of + each data point. + """ + x = np.asarray(x, dtype=float) + if x.ndim == 0: + x = x[np.newaxis] + elif x.ndim == 1: + if dim == 1: + x = x[:, np.newaxis] + else: + x = x[np.newaxis, :] + return x + + def _process_parameters(self, loc, shape, df): + """ + Infer dimensionality from location array and shape matrix, handle + defaults, and ensure compatible dimensions. + """ + if loc is None and shape is None: + loc = np.asarray(0, dtype=float) + shape = np.asarray(1, dtype=float) + dim = 1 + elif loc is None: + shape = np.asarray(shape, dtype=float) + if shape.ndim < 2: + dim = 1 + else: + dim = shape.shape[0] + loc = np.zeros(dim) + elif shape is None: + loc = np.asarray(loc, dtype=float) + dim = loc.size + shape = np.eye(dim) + else: + shape = np.asarray(shape, dtype=float) + loc = np.asarray(loc, dtype=float) + dim = loc.size + + if dim == 1: + loc = loc.reshape(1) + shape = shape.reshape(1, 1) + + if loc.ndim != 1 or loc.shape[0] != dim: + raise ValueError("Array 'loc' must be a vector of length %d." % + dim) + if shape.ndim == 0: + shape = shape * np.eye(dim) + elif shape.ndim == 1: + shape = np.diag(shape) + elif shape.ndim == 2 and shape.shape != (dim, dim): + rows, cols = shape.shape + if rows != cols: + msg = ("Array 'cov' must be square if it is two dimensional," + " but cov.shape = %s." % str(shape.shape)) + else: + msg = ("Dimension mismatch: array 'cov' is of shape %s," + " but 'loc' is a vector of length %d.") + msg = msg % (str(shape.shape), len(loc)) + raise ValueError(msg) + elif shape.ndim > 2: + raise ValueError("Array 'cov' must be at most two-dimensional," + " but cov.ndim = %d" % shape.ndim) + + # Process degrees of freedom. + if df is None: + df = 1 + elif df <= 0: + raise ValueError("'df' must be greater than zero.") + elif np.isnan(df): + raise ValueError("'df' is 'nan' but must be greater than zero or 'np.inf'.") + + return dim, loc, shape, df + + +class multivariate_t_frozen(multi_rv_frozen): + + def __init__(self, loc=None, shape=1, df=1, allow_singular=False, + seed=None): + """Create a frozen multivariate t distribution. + + Parameters + ---------- + %(_mvt_doc_default_callparams)s + + Examples + -------- + >>> import numpy as np + >>> from scipy.stats import multivariate_t + >>> loc = np.zeros(3) + >>> shape = np.eye(3) + >>> df = 10 + >>> dist = multivariate_t(loc, shape, df) + >>> dist.rvs() + array([[ 0.81412036, -1.53612361, 0.42199647]]) + >>> dist.pdf([1, 1, 1]) + array([0.01237803]) + + """ + self._dist = multivariate_t_gen(seed) + dim, loc, shape, df = self._dist._process_parameters(loc, shape, df) + self.dim, self.loc, self.shape, self.df = dim, loc, shape, df + self.shape_info = _PSD(shape, allow_singular=allow_singular) + + def logpdf(self, x): + x = self._dist._process_quantiles(x, self.dim) + U = self.shape_info.U + log_pdet = self.shape_info.log_pdet + return self._dist._logpdf(x, self.loc, U, log_pdet, self.df, self.dim, + self.shape_info.rank) + + def cdf(self, x, *, maxpts=None, lower_limit=None, random_state=None): + x = self._dist._process_quantiles(x, self.dim) + return self._dist._cdf(x, self.loc, self.shape, self.df, self.dim, + maxpts, lower_limit, random_state) + + def pdf(self, x): + return np.exp(self.logpdf(x)) + + def rvs(self, size=1, random_state=None): + return self._dist.rvs(loc=self.loc, + shape=self.shape, + df=self.df, + size=size, + random_state=random_state) + + def entropy(self): + return self._dist._entropy(self.dim, self.df, self.shape) + + +multivariate_t = multivariate_t_gen() + + +# Set frozen generator docstrings from corresponding docstrings in +# multivariate_t_gen and fill in default strings in class docstrings +for name in ['logpdf', 'pdf', 'rvs', 'cdf', 'entropy']: + method = multivariate_t_gen.__dict__[name] + method_frozen = multivariate_t_frozen.__dict__[name] + method_frozen.__doc__ = doccer.docformat(method.__doc__, + mvt_docdict_noparams) + method.__doc__ = doccer.docformat(method.__doc__, mvt_docdict_params) + + +_mhg_doc_default_callparams = """\ +m : array_like + The number of each type of object in the population. + That is, :math:`m[i]` is the number of objects of + type :math:`i`. +n : array_like + The number of samples taken from the population. +""" + +_mhg_doc_callparams_note = """\ +`m` must be an array of positive integers. If the quantile +:math:`i` contains values out of the range :math:`[0, m_i]` +where :math:`m_i` is the number of objects of type :math:`i` +in the population or if the parameters are inconsistent with one +another (e.g. ``x.sum() != n``), methods return the appropriate +value (e.g. ``0`` for ``pmf``). If `m` or `n` contain negative +values, the result will contain ``nan`` there. +""" + +_mhg_doc_frozen_callparams = "" + +_mhg_doc_frozen_callparams_note = """\ +See class definition for a detailed description of parameters.""" + +mhg_docdict_params = { + '_doc_default_callparams': _mhg_doc_default_callparams, + '_doc_callparams_note': _mhg_doc_callparams_note, + '_doc_random_state': _doc_random_state +} + +mhg_docdict_noparams = { + '_doc_default_callparams': _mhg_doc_frozen_callparams, + '_doc_callparams_note': _mhg_doc_frozen_callparams_note, + '_doc_random_state': _doc_random_state +} + + +class multivariate_hypergeom_gen(multi_rv_generic): + r"""A multivariate hypergeometric random variable. + + Methods + ------- + pmf(x, m, n) + Probability mass function. + logpmf(x, m, n) + Log of the probability mass function. + rvs(m, n, size=1, random_state=None) + Draw random samples from a multivariate hypergeometric + distribution. + mean(m, n) + Mean of the multivariate hypergeometric distribution. + var(m, n) + Variance of the multivariate hypergeometric distribution. + cov(m, n) + Compute the covariance matrix of the multivariate + hypergeometric distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + %(_doc_random_state)s + + Notes + ----- + %(_doc_callparams_note)s + + The probability mass function for `multivariate_hypergeom` is + + .. math:: + + P(X_1 = x_1, X_2 = x_2, \ldots, X_k = x_k) = \frac{\binom{m_1}{x_1} + \binom{m_2}{x_2} \cdots \binom{m_k}{x_k}}{\binom{M}{n}}, \\ \quad + (x_1, x_2, \ldots, x_k) \in \mathbb{N}^k \text{ with } + \sum_{i=1}^k x_i = n + + where :math:`m_i` are the number of objects of type :math:`i`, :math:`M` + is the total number of objects in the population (sum of all the + :math:`m_i`), and :math:`n` is the size of the sample to be taken + from the population. + + .. versionadded:: 1.6.0 + + Examples + -------- + To evaluate the probability mass function of the multivariate + hypergeometric distribution, with a dichotomous population of size + :math:`10` and :math:`20`, at a sample of size :math:`12` with + :math:`8` objects of the first type and :math:`4` objects of the + second type, use: + + >>> from scipy.stats import multivariate_hypergeom + >>> multivariate_hypergeom.pmf(x=[8, 4], m=[10, 20], n=12) + 0.0025207176631464523 + + The `multivariate_hypergeom` distribution is identical to the + corresponding `hypergeom` distribution (tiny numerical differences + notwithstanding) when only two types (good and bad) of objects + are present in the population as in the example above. Consider + another example for a comparison with the hypergeometric distribution: + + >>> from scipy.stats import hypergeom + >>> multivariate_hypergeom.pmf(x=[3, 1], m=[10, 5], n=4) + 0.4395604395604395 + >>> hypergeom.pmf(k=3, M=15, n=4, N=10) + 0.43956043956044005 + + The functions ``pmf``, ``logpmf``, ``mean``, ``var``, ``cov``, and ``rvs`` + support broadcasting, under the convention that the vector parameters + (``x``, ``m``, and ``n``) are interpreted as if each row along the last + axis is a single object. For instance, we can combine the previous two + calls to `multivariate_hypergeom` as + + >>> multivariate_hypergeom.pmf(x=[[8, 4], [3, 1]], m=[[10, 20], [10, 5]], + ... n=[12, 4]) + array([0.00252072, 0.43956044]) + + This broadcasting also works for ``cov``, where the output objects are + square matrices of size ``m.shape[-1]``. For example: + + >>> multivariate_hypergeom.cov(m=[[7, 9], [10, 15]], n=[8, 12]) + array([[[ 1.05, -1.05], + [-1.05, 1.05]], + [[ 1.56, -1.56], + [-1.56, 1.56]]]) + + That is, ``result[0]`` is equal to + ``multivariate_hypergeom.cov(m=[7, 9], n=8)`` and ``result[1]`` is equal + to ``multivariate_hypergeom.cov(m=[10, 15], n=12)``. + + Alternatively, the object may be called (as a function) to fix the `m` + and `n` parameters, returning a "frozen" multivariate hypergeometric + random variable. + + >>> rv = multivariate_hypergeom(m=[10, 20], n=12) + >>> rv.pmf(x=[8, 4]) + 0.0025207176631464523 + + See Also + -------- + scipy.stats.hypergeom : The hypergeometric distribution. + scipy.stats.multinomial : The multinomial distribution. + + References + ---------- + .. [1] The Multivariate Hypergeometric Distribution, + http://www.randomservices.org/random/urn/MultiHypergeometric.html + .. [2] Thomas J. Sargent and John Stachurski, 2020, + Multivariate Hypergeometric Distribution + https://python.quantecon.org/multi_hyper.html + """ + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__, mhg_docdict_params) + + def __call__(self, m, n, seed=None): + """Create a frozen multivariate_hypergeom distribution. + + See `multivariate_hypergeom_frozen` for more information. + """ + return multivariate_hypergeom_frozen(m, n, seed=seed) + + def _process_parameters(self, m, n): + m = np.asarray(m) + n = np.asarray(n) + if m.size == 0: + m = m.astype(int) + if n.size == 0: + n = n.astype(int) + if not np.issubdtype(m.dtype, np.integer): + raise TypeError("'m' must an array of integers.") + if not np.issubdtype(n.dtype, np.integer): + raise TypeError("'n' must an array of integers.") + if m.ndim == 0: + raise ValueError("'m' must be an array with" + " at least one dimension.") + + # check for empty arrays + if m.size != 0: + n = n[..., np.newaxis] + + m, n = np.broadcast_arrays(m, n) + + # check for empty arrays + if m.size != 0: + n = n[..., 0] + + mcond = m < 0 + + M = m.sum(axis=-1) + + ncond = (n < 0) | (n > M) + return M, m, n, mcond, ncond, np.any(mcond, axis=-1) | ncond + + def _process_quantiles(self, x, M, m, n): + x = np.asarray(x) + if not np.issubdtype(x.dtype, np.integer): + raise TypeError("'x' must an array of integers.") + if x.ndim == 0: + raise ValueError("'x' must be an array with" + " at least one dimension.") + if not x.shape[-1] == m.shape[-1]: + raise ValueError(f"Size of each quantile must be size of 'm': " + f"received {x.shape[-1]}, " + f"but expected {m.shape[-1]}.") + + # check for empty arrays + if m.size != 0: + n = n[..., np.newaxis] + M = M[..., np.newaxis] + + x, m, n, M = np.broadcast_arrays(x, m, n, M) + + # check for empty arrays + if m.size != 0: + n, M = n[..., 0], M[..., 0] + + xcond = (x < 0) | (x > m) + return (x, M, m, n, xcond, + np.any(xcond, axis=-1) | (x.sum(axis=-1) != n)) + + def _checkresult(self, result, cond, bad_value): + result = np.asarray(result) + if cond.ndim != 0: + result[cond] = bad_value + elif cond: + return bad_value + if result.ndim == 0: + return result[()] + return result + + def _logpmf(self, x, M, m, n, mxcond, ncond): + # This equation of the pmf comes from the relation, + # n combine r = beta(n+1, 1) / beta(r+1, n-r+1) + num = np.zeros_like(m, dtype=np.float64) + den = np.zeros_like(n, dtype=np.float64) + m, x = m[~mxcond], x[~mxcond] + M, n = M[~ncond], n[~ncond] + num[~mxcond] = (betaln(m+1, 1) - betaln(x+1, m-x+1)) + den[~ncond] = (betaln(M+1, 1) - betaln(n+1, M-n+1)) + num[mxcond] = np.nan + den[ncond] = np.nan + num = num.sum(axis=-1) + return num - den + + def logpmf(self, x, m, n): + """Log of the multivariate hypergeometric probability mass function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + %(_doc_default_callparams)s + + Returns + ------- + logpmf : ndarray or scalar + Log of the probability mass function evaluated at `x` + + Notes + ----- + %(_doc_callparams_note)s + """ + M, m, n, mcond, ncond, mncond = self._process_parameters(m, n) + (x, M, m, n, xcond, + xcond_reduced) = self._process_quantiles(x, M, m, n) + mxcond = mcond | xcond + ncond = ncond | np.zeros(n.shape, dtype=np.bool_) + + result = self._logpmf(x, M, m, n, mxcond, ncond) + + # replace values for which x was out of the domain; broadcast + # xcond to the right shape + xcond_ = xcond_reduced | np.zeros(mncond.shape, dtype=np.bool_) + result = self._checkresult(result, xcond_, -np.inf) + + # replace values bad for n or m; broadcast + # mncond to the right shape + mncond_ = mncond | np.zeros(xcond_reduced.shape, dtype=np.bool_) + return self._checkresult(result, mncond_, np.nan) + + def pmf(self, x, m, n): + """Multivariate hypergeometric probability mass function. + + Parameters + ---------- + x : array_like + Quantiles, with the last axis of `x` denoting the components. + %(_doc_default_callparams)s + + Returns + ------- + pmf : ndarray or scalar + Probability density function evaluated at `x` + + Notes + ----- + %(_doc_callparams_note)s + """ + out = np.exp(self.logpmf(x, m, n)) + return out + + def mean(self, m, n): + """Mean of the multivariate hypergeometric distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + mean : array_like or scalar + The mean of the distribution + """ + M, m, n, _, _, mncond = self._process_parameters(m, n) + # check for empty arrays + if m.size != 0: + M, n = M[..., np.newaxis], n[..., np.newaxis] + cond = (M == 0) + M = np.ma.masked_array(M, mask=cond) + mu = n*(m/M) + if m.size != 0: + mncond = (mncond[..., np.newaxis] | + np.zeros(mu.shape, dtype=np.bool_)) + return self._checkresult(mu, mncond, np.nan) + + def var(self, m, n): + """Variance of the multivariate hypergeometric distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + array_like + The variances of the components of the distribution. This is + the diagonal of the covariance matrix of the distribution + """ + M, m, n, _, _, mncond = self._process_parameters(m, n) + # check for empty arrays + if m.size != 0: + M, n = M[..., np.newaxis], n[..., np.newaxis] + cond = (M == 0) & (M-1 == 0) + M = np.ma.masked_array(M, mask=cond) + output = n * m/M * (M-m)/M * (M-n)/(M-1) + if m.size != 0: + mncond = (mncond[..., np.newaxis] | + np.zeros(output.shape, dtype=np.bool_)) + return self._checkresult(output, mncond, np.nan) + + def cov(self, m, n): + """Covariance matrix of the multivariate hypergeometric distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + + Returns + ------- + cov : array_like + The covariance matrix of the distribution + """ + # see [1]_ for the formula and [2]_ for implementation + # cov( x_i,x_j ) = -n * (M-n)/(M-1) * (K_i*K_j) / (M**2) + M, m, n, _, _, mncond = self._process_parameters(m, n) + # check for empty arrays + if m.size != 0: + M = M[..., np.newaxis, np.newaxis] + n = n[..., np.newaxis, np.newaxis] + cond = (M == 0) & (M-1 == 0) + M = np.ma.masked_array(M, mask=cond) + output = (-n * (M-n)/(M-1) * + np.einsum("...i,...j->...ij", m, m) / (M**2)) + # check for empty arrays + if m.size != 0: + M, n = M[..., 0, 0], n[..., 0, 0] + cond = cond[..., 0, 0] + dim = m.shape[-1] + # diagonal entries need to be computed differently + for i in range(dim): + output[..., i, i] = (n * (M-n) * m[..., i]*(M-m[..., i])) + output[..., i, i] = output[..., i, i] / (M-1) + output[..., i, i] = output[..., i, i] / (M**2) + if m.size != 0: + mncond = (mncond[..., np.newaxis, np.newaxis] | + np.zeros(output.shape, dtype=np.bool_)) + return self._checkresult(output, mncond, np.nan) + + def rvs(self, m, n, size=None, random_state=None): + """Draw random samples from a multivariate hypergeometric distribution. + + Parameters + ---------- + %(_doc_default_callparams)s + size : integer or iterable of integers, optional + Number of samples to draw. Default is ``None``, in which case a + single variate is returned as an array with shape ``m.shape``. + %(_doc_random_state)s + + Returns + ------- + rvs : array_like + Random variates of shape ``size`` or ``m.shape`` + (if ``size=None``). + + Notes + ----- + %(_doc_callparams_note)s + + Also note that NumPy's `multivariate_hypergeometric` sampler is not + used as it doesn't support broadcasting. + """ + M, m, n, _, _, _ = self._process_parameters(m, n) + + random_state = self._get_random_state(random_state) + + if size is not None and isinstance(size, int): + size = (size, ) + + if size is None: + rvs = np.empty(m.shape, dtype=m.dtype) + else: + rvs = np.empty(size + (m.shape[-1], ), dtype=m.dtype) + rem = M + + # This sampler has been taken from numpy gh-13794 + # https://github.com/numpy/numpy/pull/13794 + for c in range(m.shape[-1] - 1): + rem = rem - m[..., c] + n0mask = n == 0 + rvs[..., c] = (~n0mask * + random_state.hypergeometric(m[..., c], + rem + n0mask, + n + n0mask, + size=size)) + n = n - rvs[..., c] + rvs[..., m.shape[-1] - 1] = n + + return rvs + + +multivariate_hypergeom = multivariate_hypergeom_gen() + + +class multivariate_hypergeom_frozen(multi_rv_frozen): + def __init__(self, m, n, seed=None): + self._dist = multivariate_hypergeom_gen(seed) + (self.M, self.m, self.n, + self.mcond, self.ncond, + self.mncond) = self._dist._process_parameters(m, n) + + # monkey patch self._dist + def _process_parameters(m, n): + return (self.M, self.m, self.n, + self.mcond, self.ncond, + self.mncond) + self._dist._process_parameters = _process_parameters + + def logpmf(self, x): + return self._dist.logpmf(x, self.m, self.n) + + def pmf(self, x): + return self._dist.pmf(x, self.m, self.n) + + def mean(self): + return self._dist.mean(self.m, self.n) + + def var(self): + return self._dist.var(self.m, self.n) + + def cov(self): + return self._dist.cov(self.m, self.n) + + def rvs(self, size=1, random_state=None): + return self._dist.rvs(self.m, self.n, + size=size, + random_state=random_state) + + +# Set frozen generator docstrings from corresponding docstrings in +# multivariate_hypergeom and fill in default strings in class docstrings +for name in ['logpmf', 'pmf', 'mean', 'var', 'cov', 'rvs']: + method = multivariate_hypergeom_gen.__dict__[name] + method_frozen = multivariate_hypergeom_frozen.__dict__[name] + method_frozen.__doc__ = doccer.docformat( + method.__doc__, mhg_docdict_noparams) + method.__doc__ = doccer.docformat(method.__doc__, + mhg_docdict_params) + + +class random_table_gen(multi_rv_generic): + r"""Contingency tables from independent samples with fixed marginal sums. + + This is the distribution of random tables with given row and column vector + sums. This distribution represents the set of random tables under the null + hypothesis that rows and columns are independent. It is used in hypothesis + tests of independence. + + Because of assumed independence, the expected frequency of each table + element can be computed from the row and column sums, so that the + distribution is completely determined by these two vectors. + + Methods + ------- + logpmf(x) + Log-probability of table `x` to occur in the distribution. + pmf(x) + Probability of table `x` to occur in the distribution. + mean(row, col) + Mean table. + rvs(row, col, size=None, method=None, random_state=None) + Draw random tables with given row and column vector sums. + + Parameters + ---------- + %(_doc_row_col)s + %(_doc_random_state)s + + Notes + ----- + %(_doc_row_col_note)s + + Random elements from the distribution are generated either with Boyett's + [1]_ or Patefield's algorithm [2]_. Boyett's algorithm has + O(N) time and space complexity, where N is the total sum of entries in the + table. Patefield's algorithm has O(K x log(N)) time complexity, where K is + the number of cells in the table and requires only a small constant work + space. By default, the `rvs` method selects the fastest algorithm based on + the input, but you can specify the algorithm with the keyword `method`. + Allowed values are "boyett" and "patefield". + + .. versionadded:: 1.10.0 + + Examples + -------- + >>> from scipy.stats import random_table + + >>> row = [1, 5] + >>> col = [2, 3, 1] + >>> random_table.mean(row, col) + array([[0.33333333, 0.5 , 0.16666667], + [1.66666667, 2.5 , 0.83333333]]) + + Alternatively, the object may be called (as a function) to fix the row + and column vector sums, returning a "frozen" distribution. + + >>> dist = random_table(row, col) + >>> dist.rvs(random_state=123) + array([[1., 0., 0.], + [1., 3., 1.]]) + + References + ---------- + .. [1] J. Boyett, AS 144 Appl. Statist. 28 (1979) 329-332 + .. [2] W.M. Patefield, AS 159 Appl. Statist. 30 (1981) 91-97 + """ + + def __init__(self, seed=None): + super().__init__(seed) + + def __call__(self, row, col, *, seed=None): + """Create a frozen distribution of tables with given marginals. + + See `random_table_frozen` for more information. + """ + return random_table_frozen(row, col, seed=seed) + + def logpmf(self, x, row, col): + """Log-probability of table to occur in the distribution. + + Parameters + ---------- + %(_doc_x)s + %(_doc_row_col)s + + Returns + ------- + logpmf : ndarray or scalar + Log of the probability mass function evaluated at `x`. + + Notes + ----- + %(_doc_row_col_note)s + + If row and column marginals of `x` do not match `row` and `col`, + negative infinity is returned. + + Examples + -------- + >>> from scipy.stats import random_table + >>> import numpy as np + + >>> x = [[1, 5, 1], [2, 3, 1]] + >>> row = np.sum(x, axis=1) + >>> col = np.sum(x, axis=0) + >>> random_table.logpmf(x, row, col) + -1.6306401200847027 + + Alternatively, the object may be called (as a function) to fix the row + and column vector sums, returning a "frozen" distribution. + + >>> d = random_table(row, col) + >>> d.logpmf(x) + -1.6306401200847027 + """ + r, c, n = self._process_parameters(row, col) + x = np.asarray(x) + + if x.ndim < 2: + raise ValueError("`x` must be at least two-dimensional") + + dtype_is_int = np.issubdtype(x.dtype, np.integer) + with np.errstate(invalid='ignore'): + if not dtype_is_int and not np.all(x.astype(int) == x): + raise ValueError("`x` must contain only integral values") + + # x does not contain NaN if we arrive here + if np.any(x < 0): + raise ValueError("`x` must contain only non-negative values") + + r2 = np.sum(x, axis=-1) + c2 = np.sum(x, axis=-2) + + if r2.shape[-1] != len(r): + raise ValueError("shape of `x` must agree with `row`") + + if c2.shape[-1] != len(c): + raise ValueError("shape of `x` must agree with `col`") + + res = np.empty(x.shape[:-2]) + + mask = np.all(r2 == r, axis=-1) & np.all(c2 == c, axis=-1) + + def lnfac(x): + return gammaln(x + 1) + + res[mask] = (np.sum(lnfac(r), axis=-1) + np.sum(lnfac(c), axis=-1) + - lnfac(n) - np.sum(lnfac(x[mask]), axis=(-1, -2))) + res[~mask] = -np.inf + + return res[()] + + def pmf(self, x, row, col): + """Probability of table to occur in the distribution. + + Parameters + ---------- + %(_doc_x)s + %(_doc_row_col)s + + Returns + ------- + pmf : ndarray or scalar + Probability mass function evaluated at `x`. + + Notes + ----- + %(_doc_row_col_note)s + + If row and column marginals of `x` do not match `row` and `col`, + zero is returned. + + Examples + -------- + >>> from scipy.stats import random_table + >>> import numpy as np + + >>> x = [[1, 5, 1], [2, 3, 1]] + >>> row = np.sum(x, axis=1) + >>> col = np.sum(x, axis=0) + >>> random_table.pmf(x, row, col) + 0.19580419580419592 + + Alternatively, the object may be called (as a function) to fix the row + and column vector sums, returning a "frozen" distribution. + + >>> d = random_table(row, col) + >>> d.pmf(x) + 0.19580419580419592 + """ + return np.exp(self.logpmf(x, row, col)) + + def mean(self, row, col): + """Mean of distribution of conditional tables. + %(_doc_mean_params)s + + Returns + ------- + mean: ndarray + Mean of the distribution. + + Notes + ----- + %(_doc_row_col_note)s + + Examples + -------- + >>> from scipy.stats import random_table + + >>> row = [1, 5] + >>> col = [2, 3, 1] + >>> random_table.mean(row, col) + array([[0.33333333, 0.5 , 0.16666667], + [1.66666667, 2.5 , 0.83333333]]) + + Alternatively, the object may be called (as a function) to fix the row + and column vector sums, returning a "frozen" distribution. + + >>> d = random_table(row, col) + >>> d.mean() + array([[0.33333333, 0.5 , 0.16666667], + [1.66666667, 2.5 , 0.83333333]]) + """ + r, c, n = self._process_parameters(row, col) + return np.outer(r, c) / n + + def rvs(self, row, col, *, size=None, method=None, random_state=None): + """Draw random tables with fixed column and row marginals. + + Parameters + ---------- + %(_doc_row_col)s + size : integer, optional + Number of samples to draw (default 1). + method : str, optional + Which method to use, "boyett" or "patefield". If None (default), + selects the fastest method for this input. + %(_doc_random_state)s + + Returns + ------- + rvs : ndarray + Random 2D tables of shape (`size`, `len(row)`, `len(col)`). + + Notes + ----- + %(_doc_row_col_note)s + + Examples + -------- + >>> from scipy.stats import random_table + + >>> row = [1, 5] + >>> col = [2, 3, 1] + >>> random_table.rvs(row, col, random_state=123) + array([[1., 0., 0.], + [1., 3., 1.]]) + + Alternatively, the object may be called (as a function) to fix the row + and column vector sums, returning a "frozen" distribution. + + >>> d = random_table(row, col) + >>> d.rvs(random_state=123) + array([[1., 0., 0.], + [1., 3., 1.]]) + """ + r, c, n = self._process_parameters(row, col) + size, shape = self._process_size_shape(size, r, c) + + random_state = self._get_random_state(random_state) + meth = self._process_rvs_method(method, r, c, n) + + return meth(r, c, n, size, random_state).reshape(shape) + + @staticmethod + def _process_parameters(row, col): + """ + Check that row and column vectors are one-dimensional, that they do + not contain negative or non-integer entries, and that the sums over + both vectors are equal. + """ + r = np.array(row, dtype=np.int64, copy=True) + c = np.array(col, dtype=np.int64, copy=True) + + if np.ndim(r) != 1: + raise ValueError("`row` must be one-dimensional") + if np.ndim(c) != 1: + raise ValueError("`col` must be one-dimensional") + + if np.any(r < 0): + raise ValueError("each element of `row` must be non-negative") + if np.any(c < 0): + raise ValueError("each element of `col` must be non-negative") + + n = np.sum(r) + if n != np.sum(c): + raise ValueError("sums over `row` and `col` must be equal") + + if not np.all(r == np.asarray(row)): + raise ValueError("each element of `row` must be an integer") + if not np.all(c == np.asarray(col)): + raise ValueError("each element of `col` must be an integer") + + return r, c, n + + @staticmethod + def _process_size_shape(size, r, c): + """ + Compute the number of samples to be drawn and the shape of the output + """ + shape = (len(r), len(c)) + + if size is None: + return 1, shape + + size = np.atleast_1d(size) + if not np.issubdtype(size.dtype, np.integer) or np.any(size < 0): + raise ValueError("`size` must be a non-negative integer or `None`") + + return np.prod(size), tuple(size) + shape + + @classmethod + def _process_rvs_method(cls, method, r, c, n): + known_methods = { + None: cls._rvs_select(r, c, n), + "boyett": cls._rvs_boyett, + "patefield": cls._rvs_patefield, + } + try: + return known_methods[method] + except KeyError: + raise ValueError(f"'{method}' not recognized, " + f"must be one of {set(known_methods)}") + + @classmethod + def _rvs_select(cls, r, c, n): + fac = 1.0 # benchmarks show that this value is about 1 + k = len(r) * len(c) # number of cells + # n + 1 guards against failure if n == 0 + if n > fac * np.log(n + 1) * k: + return cls._rvs_patefield + return cls._rvs_boyett + + @staticmethod + def _rvs_boyett(row, col, ntot, size, random_state): + return _rcont.rvs_rcont1(row, col, ntot, size, random_state) + + @staticmethod + def _rvs_patefield(row, col, ntot, size, random_state): + return _rcont.rvs_rcont2(row, col, ntot, size, random_state) + + +random_table = random_table_gen() + + +class random_table_frozen(multi_rv_frozen): + def __init__(self, row, col, *, seed=None): + self._dist = random_table_gen(seed) + self._params = self._dist._process_parameters(row, col) + + # monkey patch self._dist + def _process_parameters(r, c): + return self._params + self._dist._process_parameters = _process_parameters + + def logpmf(self, x): + return self._dist.logpmf(x, None, None) + + def pmf(self, x): + return self._dist.pmf(x, None, None) + + def mean(self): + return self._dist.mean(None, None) + + def rvs(self, size=None, method=None, random_state=None): + # optimisations are possible here + return self._dist.rvs(None, None, size=size, method=method, + random_state=random_state) + + +_ctab_doc_row_col = """\ +row : array_like + Sum of table entries in each row. +col : array_like + Sum of table entries in each column.""" + +_ctab_doc_x = """\ +x : array-like + Two-dimensional table of non-negative integers, or a + multi-dimensional array with the last two dimensions + corresponding with the tables.""" + +_ctab_doc_row_col_note = """\ +The row and column vectors must be one-dimensional, not empty, +and each sum up to the same value. They cannot contain negative +or noninteger entries.""" + +_ctab_doc_mean_params = f""" +Parameters +---------- +{_ctab_doc_row_col}""" + +_ctab_doc_row_col_note_frozen = """\ +See class definition for a detailed description of parameters.""" + +_ctab_docdict = { + "_doc_random_state": _doc_random_state, + "_doc_row_col": _ctab_doc_row_col, + "_doc_x": _ctab_doc_x, + "_doc_mean_params": _ctab_doc_mean_params, + "_doc_row_col_note": _ctab_doc_row_col_note, +} + +_ctab_docdict_frozen = _ctab_docdict.copy() +_ctab_docdict_frozen.update({ + "_doc_row_col": "", + "_doc_mean_params": "", + "_doc_row_col_note": _ctab_doc_row_col_note_frozen, +}) + + +def _docfill(obj, docdict, template=None): + obj.__doc__ = doccer.docformat(template or obj.__doc__, docdict) + + +# Set frozen generator docstrings from corresponding docstrings in +# random_table and fill in default strings in class docstrings +_docfill(random_table_gen, _ctab_docdict) +for name in ['logpmf', 'pmf', 'mean', 'rvs']: + method = random_table_gen.__dict__[name] + method_frozen = random_table_frozen.__dict__[name] + _docfill(method_frozen, _ctab_docdict_frozen, method.__doc__) + _docfill(method, _ctab_docdict) + + +class uniform_direction_gen(multi_rv_generic): + r"""A vector-valued uniform direction. + + Return a random direction (unit vector). The `dim` keyword specifies + the dimensionality of the space. + + Methods + ------- + rvs(dim=None, size=1, random_state=None) + Draw random directions. + + Parameters + ---------- + dim : scalar + Dimension of directions. + seed : {None, int, `numpy.random.Generator`, + `numpy.random.RandomState`}, optional + + Used for drawing random variates. + If `seed` is `None`, the `~np.random.RandomState` singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, seeded + with seed. + If `seed` is already a ``RandomState`` or ``Generator`` instance, + then that object is used. + Default is `None`. + + Notes + ----- + This distribution generates unit vectors uniformly distributed on + the surface of a hypersphere. These can be interpreted as random + directions. + For example, if `dim` is 3, 3D vectors from the surface of :math:`S^2` + will be sampled. + + References + ---------- + .. [1] Marsaglia, G. (1972). "Choosing a Point from the Surface of a + Sphere". Annals of Mathematical Statistics. 43 (2): 645-646. + + Examples + -------- + >>> import numpy as np + >>> from scipy.stats import uniform_direction + >>> x = uniform_direction.rvs(3) + >>> np.linalg.norm(x) + 1. + + This generates one random direction, a vector on the surface of + :math:`S^2`. + + Alternatively, the object may be called (as a function) to return a frozen + distribution with fixed `dim` parameter. Here, + we create a `uniform_direction` with ``dim=3`` and draw 5 observations. + The samples are then arranged in an array of shape 5x3. + + >>> rng = np.random.default_rng() + >>> uniform_sphere_dist = uniform_direction(3) + >>> unit_vectors = uniform_sphere_dist.rvs(5, random_state=rng) + >>> unit_vectors + array([[ 0.56688642, -0.1332634 , -0.81294566], + [-0.427126 , -0.74779278, 0.50830044], + [ 0.3793989 , 0.92346629, 0.05715323], + [ 0.36428383, -0.92449076, -0.11231259], + [-0.27733285, 0.94410968, -0.17816678]]) + """ + + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__) + + def __call__(self, dim=None, seed=None): + """Create a frozen n-dimensional uniform direction distribution. + + See `uniform_direction` for more information. + """ + return uniform_direction_frozen(dim, seed=seed) + + def _process_parameters(self, dim): + """Dimension N must be specified; it cannot be inferred.""" + if dim is None or not np.isscalar(dim) or dim < 1 or dim != int(dim): + raise ValueError("Dimension of vector must be specified, " + "and must be an integer greater than 0.") + + return int(dim) + + def rvs(self, dim, size=None, random_state=None): + """Draw random samples from S(N-1). + + Parameters + ---------- + dim : integer + Dimension of space (N). + size : int or tuple of ints, optional + Given a shape of, for example, (m,n,k), m*n*k samples are + generated, and packed in an m-by-n-by-k arrangement. + Because each sample is N-dimensional, the output shape + is (m,n,k,N). If no shape is specified, a single (N-D) + sample is returned. + random_state : {None, int, `numpy.random.Generator`, + `numpy.random.RandomState`}, optional + + Pseudorandom number generator state used to generate resamples. + + If `random_state` is ``None`` (or `np.random`), the + `numpy.random.RandomState` singleton is used. + If `random_state` is an int, a new ``RandomState`` instance is + used, seeded with `random_state`. + If `random_state` is already a ``Generator`` or ``RandomState`` + instance then that instance is used. + + Returns + ------- + rvs : ndarray + Random direction vectors + + """ + random_state = self._get_random_state(random_state) + if size is None: + size = np.array([], dtype=int) + size = np.atleast_1d(size) + + dim = self._process_parameters(dim) + + samples = _sample_uniform_direction(dim, size, random_state) + return samples + + +uniform_direction = uniform_direction_gen() + + +class uniform_direction_frozen(multi_rv_frozen): + def __init__(self, dim=None, seed=None): + """Create a frozen n-dimensional uniform direction distribution. + + Parameters + ---------- + dim : int + Dimension of matrices + seed : {None, int, `numpy.random.Generator`, + `numpy.random.RandomState`}, optional + + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + + Examples + -------- + >>> from scipy.stats import uniform_direction + >>> x = uniform_direction(3) + >>> x.rvs() + + """ + self._dist = uniform_direction_gen(seed) + self.dim = self._dist._process_parameters(dim) + + def rvs(self, size=None, random_state=None): + return self._dist.rvs(self.dim, size, random_state) + + +def _sample_uniform_direction(dim, size, random_state): + """ + Private method to generate uniform directions + Reference: Marsaglia, G. (1972). "Choosing a Point from the Surface of a + Sphere". Annals of Mathematical Statistics. 43 (2): 645-646. + """ + samples_shape = np.append(size, dim) + samples = random_state.standard_normal(samples_shape) + samples /= np.linalg.norm(samples, axis=-1, keepdims=True) + return samples + + +_dirichlet_mn_doc_default_callparams = """\ +alpha : array_like + The concentration parameters. The number of entries along the last axis + determines the dimensionality of the distribution. Each entry must be + strictly positive. +n : int or array_like + The number of trials. Each element must be a strictly positive integer. +""" + +_dirichlet_mn_doc_frozen_callparams = "" + +_dirichlet_mn_doc_frozen_callparams_note = """\ +See class definition for a detailed description of parameters.""" + +dirichlet_mn_docdict_params = { + '_dirichlet_mn_doc_default_callparams': _dirichlet_mn_doc_default_callparams, + '_doc_random_state': _doc_random_state +} + +dirichlet_mn_docdict_noparams = { + '_dirichlet_mn_doc_default_callparams': _dirichlet_mn_doc_frozen_callparams, + '_doc_random_state': _doc_random_state +} + + +def _dirichlet_multinomial_check_parameters(alpha, n, x=None): + + alpha = np.asarray(alpha) + n = np.asarray(n) + + if x is not None: + # Ensure that `x` and `alpha` are arrays. If the shapes are + # incompatible, NumPy will raise an appropriate error. + try: + x, alpha = np.broadcast_arrays(x, alpha) + except ValueError as e: + msg = "`x` and `alpha` must be broadcastable." + raise ValueError(msg) from e + + x_int = np.floor(x) + if np.any(x < 0) or np.any(x != x_int): + raise ValueError("`x` must contain only non-negative integers.") + x = x_int + + if np.any(alpha <= 0): + raise ValueError("`alpha` must contain only positive values.") + + n_int = np.floor(n) + if np.any(n <= 0) or np.any(n != n_int): + raise ValueError("`n` must be a positive integer.") + n = n_int + + sum_alpha = np.sum(alpha, axis=-1) + sum_alpha, n = np.broadcast_arrays(sum_alpha, n) + + return (alpha, sum_alpha, n) if x is None else (alpha, sum_alpha, n, x) + + +class dirichlet_multinomial_gen(multi_rv_generic): + r"""A Dirichlet multinomial random variable. + + The Dirichlet multinomial distribution is a compound probability + distribution: it is the multinomial distribution with number of trials + `n` and class probabilities ``p`` randomly sampled from a Dirichlet + distribution with concentration parameters ``alpha``. + + Methods + ------- + logpmf(x, alpha, n): + Log of the probability mass function. + pmf(x, alpha, n): + Probability mass function. + mean(alpha, n): + Mean of the Dirichlet multinomial distribution. + var(alpha, n): + Variance of the Dirichlet multinomial distribution. + cov(alpha, n): + The covariance of the Dirichlet multinomial distribution. + + Parameters + ---------- + %(_dirichlet_mn_doc_default_callparams)s + %(_doc_random_state)s + + See Also + -------- + scipy.stats.dirichlet : The dirichlet distribution. + scipy.stats.multinomial : The multinomial distribution. + + References + ---------- + .. [1] Dirichlet-multinomial distribution, Wikipedia, + https://www.wikipedia.org/wiki/Dirichlet-multinomial_distribution + + Examples + -------- + >>> from scipy.stats import dirichlet_multinomial + + Get the PMF + + >>> n = 6 # number of trials + >>> alpha = [3, 4, 5] # concentration parameters + >>> x = [1, 2, 3] # counts + >>> dirichlet_multinomial.pmf(x, alpha, n) + 0.08484162895927604 + + If the sum of category counts does not equal the number of trials, + the probability mass is zero. + + >>> dirichlet_multinomial.pmf(x, alpha, n=7) + 0.0 + + Get the log of the PMF + + >>> dirichlet_multinomial.logpmf(x, alpha, n) + -2.4669689491013327 + + Get the mean + + >>> dirichlet_multinomial.mean(alpha, n) + array([1.5, 2. , 2.5]) + + Get the variance + + >>> dirichlet_multinomial.var(alpha, n) + array([1.55769231, 1.84615385, 2.01923077]) + + Get the covariance + + >>> dirichlet_multinomial.cov(alpha, n) + array([[ 1.55769231, -0.69230769, -0.86538462], + [-0.69230769, 1.84615385, -1.15384615], + [-0.86538462, -1.15384615, 2.01923077]]) + + Alternatively, the object may be called (as a function) to fix the + `alpha` and `n` parameters, returning a "frozen" Dirichlet multinomial + random variable. + + >>> dm = dirichlet_multinomial(alpha, n) + >>> dm.pmf(x) + 0.08484162895927579 + + All methods are fully vectorized. Each element of `x` and `alpha` is + a vector (along the last axis), each element of `n` is an + integer (scalar), and the result is computed element-wise. + + >>> x = [[1, 2, 3], [4, 5, 6]] + >>> alpha = [[1, 2, 3], [4, 5, 6]] + >>> n = [6, 15] + >>> dirichlet_multinomial.pmf(x, alpha, n) + array([0.06493506, 0.02626937]) + + >>> dirichlet_multinomial.cov(alpha, n).shape # both covariance matrices + (2, 3, 3) + + Broadcasting according to standard NumPy conventions is supported. Here, + we have four sets of concentration parameters (each a two element vector) + for each of three numbers of trials (each a scalar). + + >>> alpha = [[3, 4], [4, 5], [5, 6], [6, 7]] + >>> n = [[6], [7], [8]] + >>> dirichlet_multinomial.mean(alpha, n).shape + (3, 4, 2) + + """ + def __init__(self, seed=None): + super().__init__(seed) + self.__doc__ = doccer.docformat(self.__doc__, + dirichlet_mn_docdict_params) + + def __call__(self, alpha, n, seed=None): + return dirichlet_multinomial_frozen(alpha, n, seed=seed) + + def logpmf(self, x, alpha, n): + """The log of the probability mass function. + + Parameters + ---------- + x: ndarray + Category counts (non-negative integers). Must be broadcastable + with shape parameter ``alpha``. If multidimensional, the last axis + must correspond with the categories. + %(_dirichlet_mn_doc_default_callparams)s + + Returns + ------- + out: ndarray or scalar + Log of the probability mass function. + + """ + + a, Sa, n, x = _dirichlet_multinomial_check_parameters(alpha, n, x) + + out = np.asarray(loggamma(Sa) + loggamma(n + 1) - loggamma(n + Sa)) + out += (loggamma(x + a) - (loggamma(a) + loggamma(x + 1))).sum(axis=-1) + np.place(out, n != x.sum(axis=-1), -np.inf) + return out[()] + + def pmf(self, x, alpha, n): + """Probability mass function for a Dirichlet multinomial distribution. + + Parameters + ---------- + x: ndarray + Category counts (non-negative integers). Must be broadcastable + with shape parameter ``alpha``. If multidimensional, the last axis + must correspond with the categories. + %(_dirichlet_mn_doc_default_callparams)s + + Returns + ------- + out: ndarray or scalar + Probability mass function. + + """ + return np.exp(self.logpmf(x, alpha, n)) + + def mean(self, alpha, n): + """Mean of a Dirichlet multinomial distribution. + + Parameters + ---------- + %(_dirichlet_mn_doc_default_callparams)s + + Returns + ------- + out: ndarray + Mean of a Dirichlet multinomial distribution. + + """ + a, Sa, n = _dirichlet_multinomial_check_parameters(alpha, n) + n, Sa = n[..., np.newaxis], Sa[..., np.newaxis] + return n * a / Sa + + def var(self, alpha, n): + """The variance of the Dirichlet multinomial distribution. + + Parameters + ---------- + %(_dirichlet_mn_doc_default_callparams)s + + Returns + ------- + out: array_like + The variances of the components of the distribution. This is + the diagonal of the covariance matrix of the distribution. + + """ + a, Sa, n = _dirichlet_multinomial_check_parameters(alpha, n) + n, Sa = n[..., np.newaxis], Sa[..., np.newaxis] + return n * a / Sa * (1 - a/Sa) * (n + Sa) / (1 + Sa) + + def cov(self, alpha, n): + """Covariance matrix of a Dirichlet multinomial distribution. + + Parameters + ---------- + %(_dirichlet_mn_doc_default_callparams)s + + Returns + ------- + out : array_like + The covariance matrix of the distribution. + + """ + a, Sa, n = _dirichlet_multinomial_check_parameters(alpha, n) + var = dirichlet_multinomial.var(a, n) + + n, Sa = n[..., np.newaxis, np.newaxis], Sa[..., np.newaxis, np.newaxis] + aiaj = a[..., :, np.newaxis] * a[..., np.newaxis, :] + cov = -n * aiaj / Sa ** 2 * (n + Sa) / (1 + Sa) + + ii = np.arange(cov.shape[-1]) + cov[..., ii, ii] = var + return cov + + +dirichlet_multinomial = dirichlet_multinomial_gen() + + +class dirichlet_multinomial_frozen(multi_rv_frozen): + def __init__(self, alpha, n, seed=None): + alpha, Sa, n = _dirichlet_multinomial_check_parameters(alpha, n) + self.alpha = alpha + self.n = n + self._dist = dirichlet_multinomial_gen(seed) + + def logpmf(self, x): + return self._dist.logpmf(x, self.alpha, self.n) + + def pmf(self, x): + return self._dist.pmf(x, self.alpha, self.n) + + def mean(self): + return self._dist.mean(self.alpha, self.n) + + def var(self): + return self._dist.var(self.alpha, self.n) + + def cov(self): + return self._dist.cov(self.alpha, self.n) + + +# Set frozen generator docstrings from corresponding docstrings in +# dirichlet_multinomial and fill in default strings in class docstrings. +for name in ['logpmf', 'pmf', 'mean', 'var', 'cov']: + method = dirichlet_multinomial_gen.__dict__[name] + method_frozen = dirichlet_multinomial_frozen.__dict__[name] + method_frozen.__doc__ = doccer.docformat( + method.__doc__, dirichlet_mn_docdict_noparams) + method.__doc__ = doccer.docformat(method.__doc__, + dirichlet_mn_docdict_params) + + +class vonmises_fisher_gen(multi_rv_generic): + r"""A von Mises-Fisher variable. + + The `mu` keyword specifies the mean direction vector. The `kappa` keyword + specifies the concentration parameter. + + Methods + ------- + pdf(x, mu=None, kappa=1) + Probability density function. + logpdf(x, mu=None, kappa=1) + Log of the probability density function. + rvs(mu=None, kappa=1, size=1, random_state=None) + Draw random samples from a von Mises-Fisher distribution. + entropy(mu=None, kappa=1) + Compute the differential entropy of the von Mises-Fisher distribution. + fit(data) + Fit a von Mises-Fisher distribution to data. + + Parameters + ---------- + mu : array_like + Mean direction of the distribution. Must be a one-dimensional unit + vector of norm 1. + kappa : float + Concentration parameter. Must be positive. + seed : {None, int, np.random.RandomState, np.random.Generator}, optional + Used for drawing random variates. + If `seed` is `None`, the `~np.random.RandomState` singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, seeded + with seed. + If `seed` is already a ``RandomState`` or ``Generator`` instance, + then that object is used. + Default is `None`. + + See Also + -------- + scipy.stats.vonmises : Von-Mises Fisher distribution in 2D on a circle + uniform_direction : uniform distribution on the surface of a hypersphere + + Notes + ----- + The von Mises-Fisher distribution is a directional distribution on the + surface of the unit hypersphere. The probability density + function of a unit vector :math:`\mathbf{x}` is + + .. math:: + + f(\mathbf{x}) = \frac{\kappa^{d/2-1}}{(2\pi)^{d/2}I_{d/2-1}(\kappa)} + \exp\left(\kappa \mathbf{\mu}^T\mathbf{x}\right), + + where :math:`\mathbf{\mu}` is the mean direction, :math:`\kappa` the + concentration parameter, :math:`d` the dimension and :math:`I` the + modified Bessel function of the first kind. As :math:`\mu` represents + a direction, it must be a unit vector or in other words, a point + on the hypersphere: :math:`\mathbf{\mu}\in S^{d-1}`. :math:`\kappa` is a + concentration parameter, which means that it must be positive + (:math:`\kappa>0`) and that the distribution becomes more narrow with + increasing :math:`\kappa`. In that sense, the reciprocal value + :math:`1/\kappa` resembles the variance parameter of the normal + distribution. + + The von Mises-Fisher distribution often serves as an analogue of the + normal distribution on the sphere. Intuitively, for unit vectors, a + useful distance measure is given by the angle :math:`\alpha` between + them. This is exactly what the scalar product + :math:`\mathbf{\mu}^T\mathbf{x}=\cos(\alpha)` in the + von Mises-Fisher probability density function describes: the angle + between the mean direction :math:`\mathbf{\mu}` and the vector + :math:`\mathbf{x}`. The larger the angle between them, the smaller the + probability to observe :math:`\mathbf{x}` for this particular mean + direction :math:`\mathbf{\mu}`. + + In dimensions 2 and 3, specialized algorithms are used for fast sampling + [2]_, [3]_. For dimensions of 4 or higher the rejection sampling algorithm + described in [4]_ is utilized. This implementation is partially based on + the geomstats package [5]_, [6]_. + + .. versionadded:: 1.11 + + References + ---------- + .. [1] Von Mises-Fisher distribution, Wikipedia, + https://en.wikipedia.org/wiki/Von_Mises%E2%80%93Fisher_distribution + .. [2] Mardia, K., and Jupp, P. Directional statistics. Wiley, 2000. + .. [3] J. Wenzel. Numerically stable sampling of the von Mises Fisher + distribution on S2. + https://www.mitsuba-renderer.org/~wenzel/files/vmf.pdf + .. [4] Wood, A. Simulation of the von mises fisher distribution. + Communications in statistics-simulation and computation 23, + 1 (1994), 157-164. https://doi.org/10.1080/03610919408813161 + .. [5] geomstats, Github. MIT License. Accessed: 06.01.2023. + https://github.com/geomstats/geomstats + .. [6] Miolane, N. et al. Geomstats: A Python Package for Riemannian + Geometry in Machine Learning. Journal of Machine Learning Research + 21 (2020). http://jmlr.org/papers/v21/19-027.html + + Examples + -------- + **Visualization of the probability density** + + Plot the probability density in three dimensions for increasing + concentration parameter. The density is calculated by the ``pdf`` + method. + + >>> import numpy as np + >>> import matplotlib.pyplot as plt + >>> from scipy.stats import vonmises_fisher + >>> from matplotlib.colors import Normalize + >>> n_grid = 100 + >>> u = np.linspace(0, np.pi, n_grid) + >>> v = np.linspace(0, 2 * np.pi, n_grid) + >>> u_grid, v_grid = np.meshgrid(u, v) + >>> vertices = np.stack([np.cos(v_grid) * np.sin(u_grid), + ... np.sin(v_grid) * np.sin(u_grid), + ... np.cos(u_grid)], + ... axis=2) + >>> x = np.outer(np.cos(v), np.sin(u)) + >>> y = np.outer(np.sin(v), np.sin(u)) + >>> z = np.outer(np.ones_like(u), np.cos(u)) + >>> def plot_vmf_density(ax, x, y, z, vertices, mu, kappa): + ... vmf = vonmises_fisher(mu, kappa) + ... pdf_values = vmf.pdf(vertices) + ... pdfnorm = Normalize(vmin=pdf_values.min(), vmax=pdf_values.max()) + ... ax.plot_surface(x, y, z, rstride=1, cstride=1, + ... facecolors=plt.cm.viridis(pdfnorm(pdf_values)), + ... linewidth=0) + ... ax.set_aspect('equal') + ... ax.view_init(azim=-130, elev=0) + ... ax.axis('off') + ... ax.set_title(rf"$\kappa={kappa}$") + >>> fig, axes = plt.subplots(nrows=1, ncols=3, figsize=(9, 4), + ... subplot_kw={"projection": "3d"}) + >>> left, middle, right = axes + >>> mu = np.array([-np.sqrt(0.5), -np.sqrt(0.5), 0]) + >>> plot_vmf_density(left, x, y, z, vertices, mu, 5) + >>> plot_vmf_density(middle, x, y, z, vertices, mu, 20) + >>> plot_vmf_density(right, x, y, z, vertices, mu, 100) + >>> plt.subplots_adjust(top=1, bottom=0.0, left=0.0, right=1.0, wspace=0.) + >>> plt.show() + + As we increase the concentration parameter, the points are getting more + clustered together around the mean direction. + + **Sampling** + + Draw 5 samples from the distribution using the ``rvs`` method resulting + in a 5x3 array. + + >>> rng = np.random.default_rng() + >>> mu = np.array([0, 0, 1]) + >>> samples = vonmises_fisher(mu, 20).rvs(5, random_state=rng) + >>> samples + array([[ 0.3884594 , -0.32482588, 0.86231516], + [ 0.00611366, -0.09878289, 0.99509023], + [-0.04154772, -0.01637135, 0.99900239], + [-0.14613735, 0.12553507, 0.98126695], + [-0.04429884, -0.23474054, 0.97104814]]) + + These samples are unit vectors on the sphere :math:`S^2`. To verify, + let us calculate their euclidean norms: + + >>> np.linalg.norm(samples, axis=1) + array([1., 1., 1., 1., 1.]) + + Plot 20 observations drawn from the von Mises-Fisher distribution for + increasing concentration parameter :math:`\kappa`. The red dot highlights + the mean direction :math:`\mu`. + + >>> def plot_vmf_samples(ax, x, y, z, mu, kappa): + ... vmf = vonmises_fisher(mu, kappa) + ... samples = vmf.rvs(20) + ... ax.plot_surface(x, y, z, rstride=1, cstride=1, linewidth=0, + ... alpha=0.2) + ... ax.scatter(samples[:, 0], samples[:, 1], samples[:, 2], c='k', s=5) + ... ax.scatter(mu[0], mu[1], mu[2], c='r', s=30) + ... ax.set_aspect('equal') + ... ax.view_init(azim=-130, elev=0) + ... ax.axis('off') + ... ax.set_title(rf"$\kappa={kappa}$") + >>> mu = np.array([-np.sqrt(0.5), -np.sqrt(0.5), 0]) + >>> fig, axes = plt.subplots(nrows=1, ncols=3, + ... subplot_kw={"projection": "3d"}, + ... figsize=(9, 4)) + >>> left, middle, right = axes + >>> plot_vmf_samples(left, x, y, z, mu, 5) + >>> plot_vmf_samples(middle, x, y, z, mu, 20) + >>> plot_vmf_samples(right, x, y, z, mu, 100) + >>> plt.subplots_adjust(top=1, bottom=0.0, left=0.0, + ... right=1.0, wspace=0.) + >>> plt.show() + + The plots show that with increasing concentration :math:`\kappa` the + resulting samples are centered more closely around the mean direction. + + **Fitting the distribution parameters** + + The distribution can be fitted to data using the ``fit`` method returning + the estimated parameters. As a toy example let's fit the distribution to + samples drawn from a known von Mises-Fisher distribution. + + >>> mu, kappa = np.array([0, 0, 1]), 20 + >>> samples = vonmises_fisher(mu, kappa).rvs(1000, random_state=rng) + >>> mu_fit, kappa_fit = vonmises_fisher.fit(samples) + >>> mu_fit, kappa_fit + (array([0.01126519, 0.01044501, 0.99988199]), 19.306398751730995) + + We see that the estimated parameters `mu_fit` and `kappa_fit` are + very close to the ground truth parameters. + + """ + def __init__(self, seed=None): + super().__init__(seed) + + def __call__(self, mu=None, kappa=1, seed=None): + """Create a frozen von Mises-Fisher distribution. + + See `vonmises_fisher_frozen` for more information. + """ + return vonmises_fisher_frozen(mu, kappa, seed=seed) + + def _process_parameters(self, mu, kappa): + """ + Infer dimensionality from mu and ensure that mu is a one-dimensional + unit vector and kappa positive. + """ + mu = np.asarray(mu) + if mu.ndim > 1: + raise ValueError("'mu' must have one-dimensional shape.") + if not np.allclose(np.linalg.norm(mu), 1.): + raise ValueError("'mu' must be a unit vector of norm 1.") + if not mu.size > 1: + raise ValueError("'mu' must have at least two entries.") + kappa_error_msg = "'kappa' must be a positive scalar." + if not np.isscalar(kappa) or kappa < 0: + raise ValueError(kappa_error_msg) + if float(kappa) == 0.: + raise ValueError("For 'kappa=0' the von Mises-Fisher distribution " + "becomes the uniform distribution on the sphere " + "surface. Consider using " + "'scipy.stats.uniform_direction' instead.") + dim = mu.size + + return dim, mu, kappa + + def _check_data_vs_dist(self, x, dim): + if x.shape[-1] != dim: + raise ValueError("The dimensionality of the last axis of 'x' must " + "match the dimensionality of the " + "von Mises Fisher distribution.") + if not np.allclose(np.linalg.norm(x, axis=-1), 1.): + msg = "'x' must be unit vectors of norm 1 along last dimension." + raise ValueError(msg) + + def _log_norm_factor(self, dim, kappa): + # normalization factor is given by + # c = kappa**(dim/2-1)/((2*pi)**(dim/2)*I[dim/2-1](kappa)) + # = kappa**(dim/2-1)*exp(-kappa) / + # ((2*pi)**(dim/2)*I[dim/2-1](kappa)*exp(-kappa) + # = kappa**(dim/2-1)*exp(-kappa) / + # ((2*pi)**(dim/2)*ive[dim/2-1](kappa) + # Then the log is given by + # log c = 1/2*(dim -1)*log(kappa) - kappa - -1/2*dim*ln(2*pi) - + # ive[dim/2-1](kappa) + halfdim = 0.5 * dim + return (0.5 * (dim - 2)*np.log(kappa) - halfdim * _LOG_2PI - + np.log(ive(halfdim - 1, kappa)) - kappa) + + def _logpdf(self, x, dim, mu, kappa): + """Log of the von Mises-Fisher probability density function. + + As this function does no argument checking, it should not be + called directly; use 'logpdf' instead. + + """ + x = np.asarray(x) + self._check_data_vs_dist(x, dim) + dotproducts = np.einsum('i,...i->...', mu, x) + return self._log_norm_factor(dim, kappa) + kappa * dotproducts + + def logpdf(self, x, mu=None, kappa=1): + """Log of the von Mises-Fisher probability density function. + + Parameters + ---------- + x : array_like + Points at which to evaluate the log of the probability + density function. The last axis of `x` must correspond + to unit vectors of the same dimensionality as the distribution. + mu : array_like, default: None + Mean direction of the distribution. Must be a one-dimensional unit + vector of norm 1. + kappa : float, default: 1 + Concentration parameter. Must be positive. + + Returns + ------- + logpdf : ndarray or scalar + Log of the probability density function evaluated at `x`. + + """ + dim, mu, kappa = self._process_parameters(mu, kappa) + return self._logpdf(x, dim, mu, kappa) + + def pdf(self, x, mu=None, kappa=1): + """Von Mises-Fisher probability density function. + + Parameters + ---------- + x : array_like + Points at which to evaluate the probability + density function. The last axis of `x` must correspond + to unit vectors of the same dimensionality as the distribution. + mu : array_like + Mean direction of the distribution. Must be a one-dimensional unit + vector of norm 1. + kappa : float + Concentration parameter. Must be positive. + + Returns + ------- + pdf : ndarray or scalar + Probability density function evaluated at `x`. + + """ + dim, mu, kappa = self._process_parameters(mu, kappa) + return np.exp(self._logpdf(x, dim, mu, kappa)) + + def _rvs_2d(self, mu, kappa, size, random_state): + """ + In 2D, the von Mises-Fisher distribution reduces to the + von Mises distribution which can be efficiently sampled by numpy. + This method is much faster than the general rejection + sampling based algorithm. + + """ + mean_angle = np.arctan2(mu[1], mu[0]) + angle_samples = random_state.vonmises(mean_angle, kappa, size=size) + samples = np.stack([np.cos(angle_samples), np.sin(angle_samples)], + axis=-1) + return samples + + def _rvs_3d(self, kappa, size, random_state): + """ + Generate samples from a von Mises-Fisher distribution + with mu = [1, 0, 0] and kappa. Samples then have to be + rotated towards the desired mean direction mu. + This method is much faster than the general rejection + sampling based algorithm. + Reference: https://www.mitsuba-renderer.org/~wenzel/files/vmf.pdf + + """ + if size is None: + sample_size = 1 + else: + sample_size = size + + # compute x coordinate acc. to equation from section 3.1 + x = random_state.random(sample_size) + x = 1. + np.log(x + (1. - x) * np.exp(-2 * kappa))/kappa + + # (y, z) are random 2D vectors that only have to be + # normalized accordingly. Then (x, y z) follow a VMF distribution + temp = np.sqrt(1. - np.square(x)) + uniformcircle = _sample_uniform_direction(2, sample_size, random_state) + samples = np.stack([x, temp * uniformcircle[..., 0], + temp * uniformcircle[..., 1]], + axis=-1) + if size is None: + samples = np.squeeze(samples) + return samples + + def _rejection_sampling(self, dim, kappa, size, random_state): + """ + Generate samples from a n-dimensional von Mises-Fisher distribution + with mu = [1, 0, ..., 0] and kappa via rejection sampling. + Samples then have to be rotated towards the desired mean direction mu. + Reference: https://doi.org/10.1080/03610919408813161 + """ + dim_minus_one = dim - 1 + # calculate number of requested samples + if size is not None: + if not np.iterable(size): + size = (size, ) + n_samples = math.prod(size) + else: + n_samples = 1 + # calculate envelope for rejection sampler (eq. 4) + sqrt = np.sqrt(4 * kappa ** 2. + dim_minus_one ** 2) + envelop_param = (-2 * kappa + sqrt) / dim_minus_one + if envelop_param == 0: + # the regular formula suffers from loss of precision for high + # kappa. This can only be detected by checking for 0 here. + # Workaround: expansion for sqrt variable + # https://www.wolframalpha.com/input?i=sqrt%284*x%5E2%2Bd%5E2%29 + # e = (-2 * k + sqrt(k**2 + d**2)) / d + # ~ (-2 * k + 2 * k + d**2/(4 * k) - d**4/(64 * k**3)) / d + # = d/(4 * k) - d**3/(64 * k**3) + envelop_param = (dim_minus_one/4 * kappa**-1. + - dim_minus_one**3/64 * kappa**-3.) + # reference step 0 + node = (1. - envelop_param) / (1. + envelop_param) + # t = ln(1 - ((1-x)/(1+x))**2) + # = ln(4 * x / (1+x)**2) + # = ln(4) + ln(x) - 2*log1p(x) + correction = (kappa * node + dim_minus_one + * (np.log(4) + np.log(envelop_param) + - 2 * np.log1p(envelop_param))) + n_accepted = 0 + x = np.zeros((n_samples, )) + halfdim = 0.5 * dim_minus_one + # main loop + while n_accepted < n_samples: + # generate candidates acc. to reference step 1 + sym_beta = random_state.beta(halfdim, halfdim, + size=n_samples - n_accepted) + coord_x = (1 - (1 + envelop_param) * sym_beta) / ( + 1 - (1 - envelop_param) * sym_beta) + # accept or reject: reference step 2 + # reformulation for numerical stability: + # t = ln(1 - (1-x)/(1+x) * y) + # = ln((1 + x - y +x*y)/(1 +x)) + accept_tol = random_state.random(n_samples - n_accepted) + criterion = ( + kappa * coord_x + + dim_minus_one * (np.log((1 + envelop_param - coord_x + + coord_x * envelop_param) / (1 + envelop_param))) + - correction) > np.log(accept_tol) + accepted_iter = np.sum(criterion) + x[n_accepted:n_accepted + accepted_iter] = coord_x[criterion] + n_accepted += accepted_iter + # concatenate x and remaining coordinates: step 3 + coord_rest = _sample_uniform_direction(dim_minus_one, n_accepted, + random_state) + coord_rest = np.einsum( + '...,...i->...i', np.sqrt(1 - x ** 2), coord_rest) + samples = np.concatenate([x[..., None], coord_rest], axis=1) + # reshape output to (size, dim) + if size is not None: + samples = samples.reshape(size + (dim, )) + else: + samples = np.squeeze(samples) + return samples + + def _rotate_samples(self, samples, mu, dim): + """A QR decomposition is used to find the rotation that maps the + north pole (1, 0,...,0) to the vector mu. This rotation is then + applied to all samples. + + Parameters + ---------- + samples: array_like, shape = [..., n] + mu : array-like, shape=[n, ] + Point to parametrise the rotation. + + Returns + ------- + samples : rotated samples + + """ + base_point = np.zeros((dim, )) + base_point[0] = 1. + embedded = np.concatenate([mu[None, :], np.zeros((dim - 1, dim))]) + rotmatrix, _ = np.linalg.qr(np.transpose(embedded)) + if np.allclose(np.matmul(rotmatrix, base_point[:, None])[:, 0], mu): + rotsign = 1 + else: + rotsign = -1 + + # apply rotation + samples = np.einsum('ij,...j->...i', rotmatrix, samples) * rotsign + return samples + + def _rvs(self, dim, mu, kappa, size, random_state): + if dim == 2: + samples = self._rvs_2d(mu, kappa, size, random_state) + elif dim == 3: + samples = self._rvs_3d(kappa, size, random_state) + else: + samples = self._rejection_sampling(dim, kappa, size, + random_state) + + if dim != 2: + samples = self._rotate_samples(samples, mu, dim) + return samples + + def rvs(self, mu=None, kappa=1, size=1, random_state=None): + """Draw random samples from a von Mises-Fisher distribution. + + Parameters + ---------- + mu : array_like + Mean direction of the distribution. Must be a one-dimensional unit + vector of norm 1. + kappa : float + Concentration parameter. Must be positive. + size : int or tuple of ints, optional + Given a shape of, for example, (m,n,k), m*n*k samples are + generated, and packed in an m-by-n-by-k arrangement. + Because each sample is N-dimensional, the output shape + is (m,n,k,N). If no shape is specified, a single (N-D) + sample is returned. + random_state : {None, int, np.random.RandomState, np.random.Generator}, + optional + Used for drawing random variates. + If `seed` is `None`, the `~np.random.RandomState` singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, seeded + with seed. + If `seed` is already a ``RandomState`` or ``Generator`` instance, + then that object is used. + Default is `None`. + + Returns + ------- + rvs : ndarray + Random variates of shape (`size`, `N`), where `N` is the + dimension of the distribution. + + """ + dim, mu, kappa = self._process_parameters(mu, kappa) + random_state = self._get_random_state(random_state) + samples = self._rvs(dim, mu, kappa, size, random_state) + return samples + + def _entropy(self, dim, kappa): + halfdim = 0.5 * dim + return (-self._log_norm_factor(dim, kappa) - kappa * + ive(halfdim, kappa) / ive(halfdim - 1, kappa)) + + def entropy(self, mu=None, kappa=1): + """Compute the differential entropy of the von Mises-Fisher + distribution. + + Parameters + ---------- + mu : array_like, default: None + Mean direction of the distribution. Must be a one-dimensional unit + vector of norm 1. + kappa : float, default: 1 + Concentration parameter. Must be positive. + + Returns + ------- + h : scalar + Entropy of the von Mises-Fisher distribution. + + """ + dim, _, kappa = self._process_parameters(mu, kappa) + return self._entropy(dim, kappa) + + def fit(self, x): + """Fit the von Mises-Fisher distribution to data. + + Parameters + ---------- + x : array-like + Data the distribution is fitted to. Must be two dimensional. + The second axis of `x` must be unit vectors of norm 1 and + determine the dimensionality of the fitted + von Mises-Fisher distribution. + + Returns + ------- + mu : ndarray + Estimated mean direction. + kappa : float + Estimated concentration parameter. + + """ + # validate input data + x = np.asarray(x) + if x.ndim != 2: + raise ValueError("'x' must be two dimensional.") + if not np.allclose(np.linalg.norm(x, axis=-1), 1.): + msg = "'x' must be unit vectors of norm 1 along last dimension." + raise ValueError(msg) + dim = x.shape[-1] + + # mu is simply the directional mean + dirstats = directional_stats(x) + mu = dirstats.mean_direction + r = dirstats.mean_resultant_length + + # kappa is the solution to the equation: + # r = I[dim/2](kappa) / I[dim/2 -1](kappa) + # = I[dim/2](kappa) * exp(-kappa) / I[dim/2 -1](kappa) * exp(-kappa) + # = ive(dim/2, kappa) / ive(dim/2 -1, kappa) + + halfdim = 0.5 * dim + + def solve_for_kappa(kappa): + bessel_vals = ive([halfdim, halfdim - 1], kappa) + return bessel_vals[0]/bessel_vals[1] - r + + root_res = root_scalar(solve_for_kappa, method="brentq", + bracket=(1e-8, 1e9)) + kappa = root_res.root + return mu, kappa + + +vonmises_fisher = vonmises_fisher_gen() + + +class vonmises_fisher_frozen(multi_rv_frozen): + def __init__(self, mu=None, kappa=1, seed=None): + """Create a frozen von Mises-Fisher distribution. + + Parameters + ---------- + mu : array_like, default: None + Mean direction of the distribution. + kappa : float, default: 1 + Concentration parameter. Must be positive. + seed : {None, int, `numpy.random.Generator`, + `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + + """ + self._dist = vonmises_fisher_gen(seed) + self.dim, self.mu, self.kappa = ( + self._dist._process_parameters(mu, kappa) + ) + + def logpdf(self, x): + """ + Parameters + ---------- + x : array_like + Points at which to evaluate the log of the probability + density function. The last axis of `x` must correspond + to unit vectors of the same dimensionality as the distribution. + + Returns + ------- + logpdf : ndarray or scalar + Log of probability density function evaluated at `x`. + + """ + return self._dist._logpdf(x, self.dim, self.mu, self.kappa) + + def pdf(self, x): + """ + Parameters + ---------- + x : array_like + Points at which to evaluate the log of the probability + density function. The last axis of `x` must correspond + to unit vectors of the same dimensionality as the distribution. + + Returns + ------- + pdf : ndarray or scalar + Probability density function evaluated at `x`. + + """ + return np.exp(self.logpdf(x)) + + def rvs(self, size=1, random_state=None): + """Draw random variates from the Von Mises-Fisher distribution. + + Parameters + ---------- + size : int or tuple of ints, optional + Given a shape of, for example, (m,n,k), m*n*k samples are + generated, and packed in an m-by-n-by-k arrangement. + Because each sample is N-dimensional, the output shape + is (m,n,k,N). If no shape is specified, a single (N-D) + sample is returned. + random_state : {None, int, `numpy.random.Generator`, + `numpy.random.RandomState`}, optional + If `seed` is None (or `np.random`), the `numpy.random.RandomState` + singleton is used. + If `seed` is an int, a new ``RandomState`` instance is used, + seeded with `seed`. + If `seed` is already a ``Generator`` or ``RandomState`` instance + then that instance is used. + + Returns + ------- + rvs : ndarray or scalar + Random variates of size (`size`, `N`), where `N` is the + dimension of the distribution. + + """ + random_state = self._dist._get_random_state(random_state) + return self._dist._rvs(self.dim, self.mu, self.kappa, size, + random_state) + + def entropy(self): + """ + Calculate the differential entropy of the von Mises-Fisher + distribution. + + Returns + ------- + h: float + Entropy of the Von Mises-Fisher distribution. + + """ + return self._dist._entropy(self.dim, self.kappa)