python_env/lib/site-packages/pandas/tests/plotting/test_hist_method.py

""" Test cases for .hist method """
import re

import numpy as np
import pytest

from pandas import (
    DataFrame,
    Index,
    Series,
    date_range,
    to_datetime,
)
import pandas._testing as tm
from pandas.tests.plotting.common import (
    _check_ax_scales,
    _check_axes_shape,
    _check_colors,
    _check_legend_labels,
    _check_patches_all_filled,
    _check_plot_works,
    _check_text_labels,
    _check_ticks_props,
    get_x_axis,
    get_y_axis,
)

mpl = pytest.importorskip("matplotlib")


@pytest.fixture
def ts():
    return Series(
        np.arange(30, dtype=np.float64),
        index=date_range("2020-01-01", periods=30, freq="B"),
        name="ts",
    )


class TestSeriesPlots:
    @pytest.mark.parametrize("kwargs", [{}, {"grid": False}, {"figsize": (8, 10)}])
    def test_hist_legacy_kwargs(self, ts, kwargs):
        _check_plot_works(ts.hist, **kwargs)

    @pytest.mark.parametrize("kwargs", [{}, {"bins": 5}])
    def test_hist_legacy_kwargs_warning(self, ts, kwargs):
        # _check_plot_works adds an ax so catch warning. see GH #13188
        with tm.assert_produces_warning(UserWarning, check_stacklevel=False):
            _check_plot_works(ts.hist, by=ts.index.month, **kwargs)

    def test_hist_legacy_ax(self, ts):
        fig, ax = mpl.pyplot.subplots(1, 1)
        _check_plot_works(ts.hist, ax=ax, default_axes=True)

    def test_hist_legacy_ax_and_fig(self, ts):
        fig, ax = mpl.pyplot.subplots(1, 1)
        _check_plot_works(ts.hist, ax=ax, figure=fig, default_axes=True)

    def test_hist_legacy_fig(self, ts):
        fig, _ = mpl.pyplot.subplots(1, 1)
        _check_plot_works(ts.hist, figure=fig, default_axes=True)

    def test_hist_legacy_multi_ax(self, ts):
        fig, (ax1, ax2) = mpl.pyplot.subplots(1, 2)
        _check_plot_works(ts.hist, figure=fig, ax=ax1, default_axes=True)
        _check_plot_works(ts.hist, figure=fig, ax=ax2, default_axes=True)

    def test_hist_legacy_by_fig_error(self, ts):
        fig, _ = mpl.pyplot.subplots(1, 1)
        msg = (
            "Cannot pass 'figure' when using the 'by' argument, since a new 'Figure' "
            "instance will be created"
        )
        with pytest.raises(ValueError, match=msg):
            ts.hist(by=ts.index, figure=fig)

    def test_hist_bins_legacy(self):
        df = DataFrame(np.random.default_rng(2).standard_normal((10, 2)))
        ax = df.hist(bins=2)[0][0]
        assert len(ax.patches) == 2

    def test_hist_layout(self, hist_df):
        df = hist_df
        msg = "The 'layout' keyword is not supported when 'by' is None"
        with pytest.raises(ValueError, match=msg):
            df.height.hist(layout=(1, 1))

        with pytest.raises(ValueError, match=msg):
            df.height.hist(layout=[1, 1])

    @pytest.mark.slow
    @pytest.mark.parametrize(
        "by, layout, axes_num, res_layout",
        [
            ["gender", (2, 1), 2, (2, 1)],
            ["gender", (3, -1), 2, (3, 1)],
            ["category", (4, 1), 4, (4, 1)],
            ["category", (2, -1), 4, (2, 2)],
            ["category", (3, -1), 4, (3, 2)],
            ["category", (-1, 4), 4, (1, 4)],
            ["classroom", (2, 2), 3, (2, 2)],
        ],
    )
    def test_hist_layout_with_by(self, hist_df, by, layout, axes_num, res_layout):
        df = hist_df

        # _check_plot_works adds an `ax` kwarg to the method call
        # so we get a warning about an axis being cleared, even
        # though we don't explicing pass one, see GH #13188
        with tm.assert_produces_warning(UserWarning, check_stacklevel=False):
            axes = _check_plot_works(df.height.hist, by=getattr(df, by), layout=layout)
        _check_axes_shape(axes, axes_num=axes_num, layout=res_layout)

    def test_hist_layout_with_by_shape(self, hist_df):
        df = hist_df

        axes = df.height.hist(by=df.category, layout=(4, 2), figsize=(12, 7))
        _check_axes_shape(axes, axes_num=4, layout=(4, 2), figsize=(12, 7))

    def test_hist_no_overlap(self):
        from matplotlib.pyplot import (
            gcf,
            subplot,
        )

        x = Series(np.random.default_rng(2).standard_normal(2))
        y = Series(np.random.default_rng(2).standard_normal(2))
        subplot(121)
        x.hist()
        subplot(122)
        y.hist()
        fig = gcf()
        axes = fig.axes
        assert len(axes) == 2

    def test_hist_by_no_extra_plots(self, hist_df):
        df = hist_df
        df.height.hist(by=df.gender)
        assert len(mpl.pyplot.get_fignums()) == 1

    def test_plot_fails_when_ax_differs_from_figure(self, ts):
        from pylab import figure

        fig1 = figure()
        fig2 = figure()
        ax1 = fig1.add_subplot(111)
        msg = "passed axis not bound to passed figure"
        with pytest.raises(AssertionError, match=msg):
            ts.hist(ax=ax1, figure=fig2)

    @pytest.mark.parametrize(
        "histtype, expected",
        [
            ("bar", True),
            ("barstacked", True),
            ("step", False),
            ("stepfilled", True),
        ],
    )
    def test_histtype_argument(self, histtype, expected):
        # GH23992 Verify functioning of histtype argument
        ser = Series(np.random.default_rng(2).integers(1, 10))
        ax = ser.hist(histtype=histtype)
        _check_patches_all_filled(ax, filled=expected)

    @pytest.mark.parametrize(
        "by, expected_axes_num, expected_layout", [(None, 1, (1, 1)), ("b", 2, (1, 2))]
    )
    def test_hist_with_legend(self, by, expected_axes_num, expected_layout):
        # GH 6279 - Series histogram can have a legend
        index = 15 * ["1"] + 15 * ["2"]
        s = Series(np.random.default_rng(2).standard_normal(30), index=index, name="a")
        s.index.name = "b"

        # Use default_axes=True when plotting method generate subplots itself
        axes = _check_plot_works(s.hist, default_axes=True, legend=True, by=by)
        _check_axes_shape(axes, axes_num=expected_axes_num, layout=expected_layout)
        _check_legend_labels(axes, "a")

    @pytest.mark.parametrize("by", [None, "b"])
    def test_hist_with_legend_raises(self, by):
        # GH 6279 - Series histogram with legend and label raises
        index = 15 * ["1"] + 15 * ["2"]
        s = Series(np.random.default_rng(2).standard_normal(30), index=index, name="a")
        s.index.name = "b"

        with pytest.raises(ValueError, match="Cannot use both legend and label"):
            s.hist(legend=True, by=by, label="c")

    def test_hist_kwargs(self, ts):
        _, ax = mpl.pyplot.subplots()
        ax = ts.plot.hist(bins=5, ax=ax)
        assert len(ax.patches) == 5
        _check_text_labels(ax.yaxis.get_label(), "Frequency")

    def test_hist_kwargs_horizontal(self, ts):
        _, ax = mpl.pyplot.subplots()
        ax = ts.plot.hist(bins=5, ax=ax)
        ax = ts.plot.hist(orientation="horizontal", ax=ax)
        _check_text_labels(ax.xaxis.get_label(), "Frequency")

    def test_hist_kwargs_align(self, ts):
        _, ax = mpl.pyplot.subplots()
        ax = ts.plot.hist(bins=5, ax=ax)
        ax = ts.plot.hist(align="left", stacked=True, ax=ax)

    @pytest.mark.xfail(reason="Api changed in 3.6.0")
    def test_hist_kde(self, ts):
        pytest.importorskip("scipy")
        _, ax = mpl.pyplot.subplots()
        ax = ts.plot.hist(logy=True, ax=ax)
        _check_ax_scales(ax, yaxis="log")
        xlabels = ax.get_xticklabels()
        # ticks are values, thus ticklabels are blank
        _check_text_labels(xlabels, [""] * len(xlabels))
        ylabels = ax.get_yticklabels()
        _check_text_labels(ylabels, [""] * len(ylabels))

    def test_hist_kde_plot_works(self, ts):
        pytest.importorskip("scipy")
        _check_plot_works(ts.plot.kde)

    def test_hist_kde_density_works(self, ts):
        pytest.importorskip("scipy")
        _check_plot_works(ts.plot.density)

    @pytest.mark.xfail(reason="Api changed in 3.6.0")
    def test_hist_kde_logy(self, ts):
        pytest.importorskip("scipy")
        _, ax = mpl.pyplot.subplots()
        ax = ts.plot.kde(logy=True, ax=ax)
        _check_ax_scales(ax, yaxis="log")
        xlabels = ax.get_xticklabels()
        _check_text_labels(xlabels, [""] * len(xlabels))
        ylabels = ax.get_yticklabels()
        _check_text_labels(ylabels, [""] * len(ylabels))

    def test_hist_kde_color_bins(self, ts):
        pytest.importorskip("scipy")
        _, ax = mpl.pyplot.subplots()
        ax = ts.plot.hist(logy=True, bins=10, color="b", ax=ax)
        _check_ax_scales(ax, yaxis="log")
        assert len(ax.patches) == 10
        _check_colors(ax.patches, facecolors=["b"] * 10)

    def test_hist_kde_color(self, ts):
        pytest.importorskip("scipy")
        _, ax = mpl.pyplot.subplots()
        ax = ts.plot.kde(logy=True, color="r", ax=ax)
        _check_ax_scales(ax, yaxis="log")
        lines = ax.get_lines()
        assert len(lines) == 1
        _check_colors(lines, ["r"])


class TestDataFramePlots:
    @pytest.mark.slow
    def test_hist_df_legacy(self, hist_df):
        with tm.assert_produces_warning(UserWarning, check_stacklevel=False):
            _check_plot_works(hist_df.hist)

    @pytest.mark.slow
    def test_hist_df_legacy_layout(self):
        # make sure layout is handled
        df = DataFrame(np.random.default_rng(2).standard_normal((10, 2)))
        df[2] = to_datetime(
            np.random.default_rng(2).integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        with tm.assert_produces_warning(UserWarning, check_stacklevel=False):
            axes = _check_plot_works(df.hist, grid=False)
        _check_axes_shape(axes, axes_num=3, layout=(2, 2))
        assert not axes[1, 1].get_visible()

        _check_plot_works(df[[2]].hist)

    @pytest.mark.slow
    def test_hist_df_legacy_layout2(self):
        df = DataFrame(np.random.default_rng(2).standard_normal((10, 1)))
        _check_plot_works(df.hist)

    @pytest.mark.slow
    def test_hist_df_legacy_layout3(self):
        # make sure layout is handled
        df = DataFrame(np.random.default_rng(2).standard_normal((10, 5)))
        df[5] = to_datetime(
            np.random.default_rng(2).integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        with tm.assert_produces_warning(UserWarning, check_stacklevel=False):
            axes = _check_plot_works(df.hist, layout=(4, 2))
        _check_axes_shape(axes, axes_num=6, layout=(4, 2))

    @pytest.mark.slow
    @pytest.mark.parametrize(
        "kwargs", [{"sharex": True, "sharey": True}, {"figsize": (8, 10)}, {"bins": 5}]
    )
    def test_hist_df_legacy_layout_kwargs(self, kwargs):
        df = DataFrame(np.random.default_rng(2).standard_normal((10, 5)))
        df[5] = to_datetime(
            np.random.default_rng(2).integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        # make sure sharex, sharey is handled
        # handle figsize arg
        # check bins argument
        with tm.assert_produces_warning(UserWarning, check_stacklevel=False):
            _check_plot_works(df.hist, **kwargs)

    @pytest.mark.slow
    def test_hist_df_legacy_layout_labelsize_rot(self, frame_or_series):
        # make sure xlabelsize and xrot are handled
        obj = frame_or_series(range(10))
        xf, yf = 20, 18
        xrot, yrot = 30, 40
        axes = obj.hist(xlabelsize=xf, xrot=xrot, ylabelsize=yf, yrot=yrot)
        _check_ticks_props(axes, xlabelsize=xf, xrot=xrot, ylabelsize=yf, yrot=yrot)

    @pytest.mark.slow
    def test_hist_df_legacy_rectangles(self):
        from matplotlib.patches import Rectangle

        ser = Series(range(10))
        ax = ser.hist(cumulative=True, bins=4, density=True)
        # height of last bin (index 5) must be 1.0
        rects = [x for x in ax.get_children() if isinstance(x, Rectangle)]
        tm.assert_almost_equal(rects[-1].get_height(), 1.0)

    @pytest.mark.slow
    def test_hist_df_legacy_scale(self):
        ser = Series(range(10))
        ax = ser.hist(log=True)
        # scale of y must be 'log'
        _check_ax_scales(ax, yaxis="log")

    @pytest.mark.slow
    def test_hist_df_legacy_external_error(self):
        ser = Series(range(10))
        # propagate attr exception from matplotlib.Axes.hist
        with tm.external_error_raised(AttributeError):
            ser.hist(foo="bar")

    def test_hist_non_numerical_or_datetime_raises(self):
        # gh-10444, GH32590
        df = DataFrame(
            {
                "a": np.random.default_rng(2).random(10),
                "b": np.random.default_rng(2).integers(0, 10, 10),
                "c": to_datetime(
                    np.random.default_rng(2).integers(
                        1582800000000000000, 1583500000000000000, 10, dtype=np.int64
                    )
                ),
                "d": to_datetime(
                    np.random.default_rng(2).integers(
                        1582800000000000000, 1583500000000000000, 10, dtype=np.int64
                    ),
                    utc=True,
                ),
            }
        )
        df_o = df.astype(object)

        msg = "hist method requires numerical or datetime columns, nothing to plot."
        with pytest.raises(ValueError, match=msg):
            df_o.hist()

    @pytest.mark.parametrize(
        "layout_test",
        (
            {"layout": None, "expected_size": (2, 2)},  # default is 2x2
            {"layout": (2, 2), "expected_size": (2, 2)},
            {"layout": (4, 1), "expected_size": (4, 1)},
            {"layout": (1, 4), "expected_size": (1, 4)},
            {"layout": (3, 3), "expected_size": (3, 3)},
            {"layout": (-1, 4), "expected_size": (1, 4)},
            {"layout": (4, -1), "expected_size": (4, 1)},
            {"layout": (-1, 2), "expected_size": (2, 2)},
            {"layout": (2, -1), "expected_size": (2, 2)},
        ),
    )
    def test_hist_layout(self, layout_test):
        df = DataFrame(np.random.default_rng(2).standard_normal((10, 2)))
        df[2] = to_datetime(
            np.random.default_rng(2).integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        axes = df.hist(layout=layout_test["layout"])
        expected = layout_test["expected_size"]
        _check_axes_shape(axes, axes_num=3, layout=expected)

    def test_hist_layout_error(self):
        df = DataFrame(np.random.default_rng(2).standard_normal((10, 2)))
        df[2] = to_datetime(
            np.random.default_rng(2).integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        # layout too small for all 4 plots
        msg = "Layout of 1x1 must be larger than required size 3"
        with pytest.raises(ValueError, match=msg):
            df.hist(layout=(1, 1))

        # invalid format for layout
        msg = re.escape("Layout must be a tuple of (rows, columns)")
        with pytest.raises(ValueError, match=msg):
            df.hist(layout=(1,))
        msg = "At least one dimension of layout must be positive"
        with pytest.raises(ValueError, match=msg):
            df.hist(layout=(-1, -1))

    # GH 9351
    def test_tight_layout(self):
        df = DataFrame(np.random.default_rng(2).standard_normal((100, 2)))
        df[2] = to_datetime(
            np.random.default_rng(2).integers(
                812419200000000000,
                819331200000000000,
                size=100,
                dtype=np.int64,
            )
        )
        # Use default_axes=True when plotting method generate subplots itself
        _check_plot_works(df.hist, default_axes=True)
        mpl.pyplot.tight_layout()

    def test_hist_subplot_xrot(self):
        # GH 30288
        df = DataFrame(
            {
                "length": [1.5, 0.5, 1.2, 0.9, 3],
                "animal": ["pig", "rabbit", "pig", "pig", "rabbit"],
            }
        )
        # Use default_axes=True when plotting method generate subplots itself
        axes = _check_plot_works(
            df.hist,
            default_axes=True,
            column="length",
            by="animal",
            bins=5,
            xrot=0,
        )
        _check_ticks_props(axes, xrot=0)

    @pytest.mark.parametrize(
        "column, expected",
        [
            (None, ["width", "length", "height"]),
            (["length", "width", "height"], ["length", "width", "height"]),
        ],
    )
    def test_hist_column_order_unchanged(self, column, expected):
        # GH29235

        df = DataFrame(
            {
                "width": [0.7, 0.2, 0.15, 0.2, 1.1],
                "length": [1.5, 0.5, 1.2, 0.9, 3],
                "height": [3, 0.5, 3.4, 2, 1],
            },
            index=["pig", "rabbit", "duck", "chicken", "horse"],
        )

        # Use default_axes=True when plotting method generate subplots itself
        axes = _check_plot_works(
            df.hist,
            default_axes=True,
            column=column,
            layout=(1, 3),
        )
        result = [axes[0, i].get_title() for i in range(3)]
        assert result == expected

    @pytest.mark.parametrize(
        "histtype, expected",
        [
            ("bar", True),
            ("barstacked", True),
            ("step", False),
            ("stepfilled", True),
        ],
    )
    def test_histtype_argument(self, histtype, expected):
        # GH23992 Verify functioning of histtype argument
        df = DataFrame(
            np.random.default_rng(2).integers(1, 10, size=(100, 2)), columns=["a", "b"]
        )
        ax = df.hist(histtype=histtype)
        _check_patches_all_filled(ax, filled=expected)

    @pytest.mark.parametrize("by", [None, "c"])
    @pytest.mark.parametrize("column", [None, "b"])
    def test_hist_with_legend(self, by, column):
        # GH 6279 - DataFrame histogram can have a legend
        expected_axes_num = 1 if by is None and column is not None else 2
        expected_layout = (1, expected_axes_num)
        expected_labels = column or ["a", "b"]
        if by is not None:
            expected_labels = [expected_labels] * 2

        index = Index(15 * ["1"] + 15 * ["2"], name="c")
        df = DataFrame(
            np.random.default_rng(2).standard_normal((30, 2)),
            index=index,
            columns=["a", "b"],
        )

        # Use default_axes=True when plotting method generate subplots itself
        axes = _check_plot_works(
            df.hist,
            default_axes=True,
            legend=True,
            by=by,
            column=column,
        )

        _check_axes_shape(axes, axes_num=expected_axes_num, layout=expected_layout)
        if by is None and column is None:
            axes = axes[0]
        for expected_label, ax in zip(expected_labels, axes):
            _check_legend_labels(ax, expected_label)

    @pytest.mark.parametrize("by", [None, "c"])
    @pytest.mark.parametrize("column", [None, "b"])
    def test_hist_with_legend_raises(self, by, column):
        # GH 6279 - DataFrame histogram with legend and label raises
        index = Index(15 * ["1"] + 15 * ["2"], name="c")
        df = DataFrame(
            np.random.default_rng(2).standard_normal((30, 2)),
            index=index,
            columns=["a", "b"],
        )

        with pytest.raises(ValueError, match="Cannot use both legend and label"):
            df.hist(legend=True, by=by, column=column, label="d")

    def test_hist_df_kwargs(self):
        df = DataFrame(np.random.default_rng(2).standard_normal((10, 2)))
        _, ax = mpl.pyplot.subplots()
        ax = df.plot.hist(bins=5, ax=ax)
        assert len(ax.patches) == 10

    def test_hist_df_with_nonnumerics(self):
        # GH 9853
        df = DataFrame(
            np.random.default_rng(2).standard_normal((10, 4)),
            columns=["A", "B", "C", "D"],
        )
        df["E"] = ["x", "y"] * 5
        _, ax = mpl.pyplot.subplots()
        ax = df.plot.hist(bins=5, ax=ax)
        assert len(ax.patches) == 20

    def test_hist_df_with_nonnumerics_no_bins(self):
        # GH 9853
        df = DataFrame(
            np.random.default_rng(2).standard_normal((10, 4)),
            columns=["A", "B", "C", "D"],
        )
        df["E"] = ["x", "y"] * 5
        _, ax = mpl.pyplot.subplots()
        ax = df.plot.hist(ax=ax)  # bins=10
        assert len(ax.patches) == 40

    def test_hist_secondary_legend(self):
        # GH 9610
        df = DataFrame(
            np.random.default_rng(2).standard_normal((30, 4)), columns=list("abcd")
        )

        # primary -> secondary
        _, ax = mpl.pyplot.subplots()
        ax = df["a"].plot.hist(legend=True, ax=ax)
        df["b"].plot.hist(ax=ax, legend=True, secondary_y=True)
        # both legends are drawn on left ax
        # left and right axis must be visible
        _check_legend_labels(ax, labels=["a", "b (right)"])
        assert ax.get_yaxis().get_visible()
        assert ax.right_ax.get_yaxis().get_visible()

    def test_hist_secondary_secondary(self):
        # GH 9610
        df = DataFrame(
            np.random.default_rng(2).standard_normal((30, 4)), columns=list("abcd")
        )
        # secondary -> secondary
        _, ax = mpl.pyplot.subplots()
        ax = df["a"].plot.hist(legend=True, secondary_y=True, ax=ax)
        df["b"].plot.hist(ax=ax, legend=True, secondary_y=True)
        # both legends are draw on left ax
        # left axis must be invisible, right axis must be visible
        _check_legend_labels(ax.left_ax, labels=["a (right)", "b (right)"])
        assert not ax.left_ax.get_yaxis().get_visible()
        assert ax.get_yaxis().get_visible()

    def test_hist_secondary_primary(self):
        # GH 9610
        df = DataFrame(
            np.random.default_rng(2).standard_normal((30, 4)), columns=list("abcd")
        )
        # secondary -> primary
        _, ax = mpl.pyplot.subplots()
        ax = df["a"].plot.hist(legend=True, secondary_y=True, ax=ax)
        # right axes is returned
        df["b"].plot.hist(ax=ax, legend=True)
        # both legends are draw on left ax
        # left and right axis must be visible
        _check_legend_labels(ax.left_ax, labels=["a (right)", "b"])
        assert ax.left_ax.get_yaxis().get_visible()
        assert ax.get_yaxis().get_visible()

    def test_hist_with_nans_and_weights(self):
        # GH 48884
        mpl_patches = pytest.importorskip("matplotlib.patches")
        df = DataFrame(
            [[np.nan, 0.2, 0.3], [0.4, np.nan, np.nan], [0.7, 0.8, 0.9]],
            columns=list("abc"),
        )
        weights = np.array([0.25, 0.3, 0.45])
        no_nan_df = DataFrame([[0.4, 0.2, 0.3], [0.7, 0.8, 0.9]], columns=list("abc"))
        no_nan_weights = np.array([[0.3, 0.25, 0.25], [0.45, 0.45, 0.45]])

        _, ax0 = mpl.pyplot.subplots()
        df.plot.hist(ax=ax0, weights=weights)
        rects = [x for x in ax0.get_children() if isinstance(x, mpl_patches.Rectangle)]
        heights = [rect.get_height() for rect in rects]
        _, ax1 = mpl.pyplot.subplots()
        no_nan_df.plot.hist(ax=ax1, weights=no_nan_weights)
        no_nan_rects = [
            x for x in ax1.get_children() if isinstance(x, mpl_patches.Rectangle)
        ]
        no_nan_heights = [rect.get_height() for rect in no_nan_rects]
        assert all(h0 == h1 for h0, h1 in zip(heights, no_nan_heights))

        idxerror_weights = np.array([[0.3, 0.25], [0.45, 0.45]])

        msg = "weights must have the same shape as data, or be a single column"
        with pytest.raises(ValueError, match=msg):
            _, ax2 = mpl.pyplot.subplots()
            no_nan_df.plot.hist(ax=ax2, weights=idxerror_weights)


class TestDataFrameGroupByPlots:
    def test_grouped_hist_legacy(self):
        from pandas.plotting._matplotlib.hist import _grouped_hist

        rs = np.random.default_rng(10)
        df = DataFrame(rs.standard_normal((10, 1)), columns=["A"])
        df["B"] = to_datetime(
            rs.integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        df["C"] = rs.integers(0, 4, 10)
        df["D"] = ["X"] * 10

        axes = _grouped_hist(df.A, by=df.C)
        _check_axes_shape(axes, axes_num=4, layout=(2, 2))

    def test_grouped_hist_legacy_axes_shape_no_col(self):
        rs = np.random.default_rng(10)
        df = DataFrame(rs.standard_normal((10, 1)), columns=["A"])
        df["B"] = to_datetime(
            rs.integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        df["C"] = rs.integers(0, 4, 10)
        df["D"] = ["X"] * 10
        axes = df.hist(by=df.C)
        _check_axes_shape(axes, axes_num=4, layout=(2, 2))

    def test_grouped_hist_legacy_single_key(self):
        rs = np.random.default_rng(2)
        df = DataFrame(rs.standard_normal((10, 1)), columns=["A"])
        df["B"] = to_datetime(
            rs.integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        df["C"] = rs.integers(0, 4, 10)
        df["D"] = ["X"] * 10
        # group by a key with single value
        axes = df.hist(by="D", rot=30)
        _check_axes_shape(axes, axes_num=1, layout=(1, 1))
        _check_ticks_props(axes, xrot=30)

    def test_grouped_hist_legacy_grouped_hist_kwargs(self):
        from matplotlib.patches import Rectangle

        from pandas.plotting._matplotlib.hist import _grouped_hist

        rs = np.random.default_rng(2)
        df = DataFrame(rs.standard_normal((10, 1)), columns=["A"])
        df["B"] = to_datetime(
            rs.integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        df["C"] = rs.integers(0, 4, 10)
        # make sure kwargs to hist are handled
        xf, yf = 20, 18
        xrot, yrot = 30, 40

        axes = _grouped_hist(
            df.A,
            by=df.C,
            cumulative=True,
            bins=4,
            xlabelsize=xf,
            xrot=xrot,
            ylabelsize=yf,
            yrot=yrot,
            density=True,
        )
        # height of last bin (index 5) must be 1.0
        for ax in axes.ravel():
            rects = [x for x in ax.get_children() if isinstance(x, Rectangle)]
            height = rects[-1].get_height()
            tm.assert_almost_equal(height, 1.0)
        _check_ticks_props(axes, xlabelsize=xf, xrot=xrot, ylabelsize=yf, yrot=yrot)

    def test_grouped_hist_legacy_grouped_hist(self):
        from pandas.plotting._matplotlib.hist import _grouped_hist

        rs = np.random.default_rng(2)
        df = DataFrame(rs.standard_normal((10, 1)), columns=["A"])
        df["B"] = to_datetime(
            rs.integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        df["C"] = rs.integers(0, 4, 10)
        df["D"] = ["X"] * 10
        axes = _grouped_hist(df.A, by=df.C, log=True)
        # scale of y must be 'log'
        _check_ax_scales(axes, yaxis="log")

    def test_grouped_hist_legacy_external_err(self):
        from pandas.plotting._matplotlib.hist import _grouped_hist

        rs = np.random.default_rng(2)
        df = DataFrame(rs.standard_normal((10, 1)), columns=["A"])
        df["B"] = to_datetime(
            rs.integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        df["C"] = rs.integers(0, 4, 10)
        df["D"] = ["X"] * 10
        # propagate attr exception from matplotlib.Axes.hist
        with tm.external_error_raised(AttributeError):
            _grouped_hist(df.A, by=df.C, foo="bar")

    def test_grouped_hist_legacy_figsize_err(self):
        rs = np.random.default_rng(2)
        df = DataFrame(rs.standard_normal((10, 1)), columns=["A"])
        df["B"] = to_datetime(
            rs.integers(
                812419200000000000,
                819331200000000000,
                size=10,
                dtype=np.int64,
            )
        )
        df["C"] = rs.integers(0, 4, 10)
        df["D"] = ["X"] * 10
        msg = "Specify figure size by tuple instead"
        with pytest.raises(ValueError, match=msg):
            df.hist(by="C", figsize="default")

    def test_grouped_hist_legacy2(self):
        n = 10
        weight = Series(np.random.default_rng(2).normal(166, 20, size=n))
        height = Series(np.random.default_rng(2).normal(60, 10, size=n))
        gender_int = np.random.default_rng(2).choice([0, 1], size=n)
        df_int = DataFrame({"height": height, "weight": weight, "gender": gender_int})
        gb = df_int.groupby("gender")
        axes = gb.hist()
        assert len(axes) == 2
        assert len(mpl.pyplot.get_fignums()) == 2

    @pytest.mark.slow
    @pytest.mark.parametrize(
        "msg, plot_col, by_col, layout",
        [
            [
                "Layout of 1x1 must be larger than required size 2",
                "weight",
                "gender",
                (1, 1),
            ],
            [
                "Layout of 1x3 must be larger than required size 4",
                "height",
                "category",
                (1, 3),
            ],
            [
                "At least one dimension of layout must be positive",
                "height",
                "category",
                (-1, -1),
            ],
        ],
    )
    def test_grouped_hist_layout_error(self, hist_df, msg, plot_col, by_col, layout):
        df = hist_df
        with pytest.raises(ValueError, match=msg):
            df.hist(column=plot_col, by=getattr(df, by_col), layout=layout)

    @pytest.mark.slow
    def test_grouped_hist_layout_warning(self, hist_df):
        df = hist_df
        with tm.assert_produces_warning(UserWarning, check_stacklevel=False):
            axes = _check_plot_works(
                df.hist, column="height", by=df.gender, layout=(2, 1)
            )
        _check_axes_shape(axes, axes_num=2, layout=(2, 1))

    @pytest.mark.slow
    @pytest.mark.parametrize(
        "layout, check_layout, figsize",
        [[(4, 1), (4, 1), None], [(-1, 1), (4, 1), None], [(4, 2), (4, 2), (12, 8)]],
    )
    def test_grouped_hist_layout_figsize(self, hist_df, layout, check_layout, figsize):
        df = hist_df
        axes = df.hist(column="height", by=df.category, layout=layout, figsize=figsize)
        _check_axes_shape(axes, axes_num=4, layout=check_layout, figsize=figsize)

    @pytest.mark.slow
    @pytest.mark.parametrize("kwargs", [{}, {"column": "height", "layout": (2, 2)}])
    def test_grouped_hist_layout_by_warning(self, hist_df, kwargs):
        df = hist_df
        # GH 6769
        with tm.assert_produces_warning(UserWarning, check_stacklevel=False):
            axes = _check_plot_works(df.hist, by="classroom", **kwargs)
        _check_axes_shape(axes, axes_num=3, layout=(2, 2))

    @pytest.mark.slow
    @pytest.mark.parametrize(
        "kwargs, axes_num, layout",
        [
            [{"by": "gender", "layout": (3, 5)}, 2, (3, 5)],
            [{"column": ["height", "weight", "category"]}, 3, (2, 2)],
        ],
    )
    def test_grouped_hist_layout_axes(self, hist_df, kwargs, axes_num, layout):
        df = hist_df
        axes = df.hist(**kwargs)
        _check_axes_shape(axes, axes_num=axes_num, layout=layout)

    def test_grouped_hist_multiple_axes(self, hist_df):
        # GH 6970, GH 7069
        df = hist_df

        fig, axes = mpl.pyplot.subplots(2, 3)
        returned = df.hist(column=["height", "weight", "category"], ax=axes[0])
        _check_axes_shape(returned, axes_num=3, layout=(1, 3))
        tm.assert_numpy_array_equal(returned, axes[0])
        assert returned[0].figure is fig

    def test_grouped_hist_multiple_axes_no_cols(self, hist_df):
        # GH 6970, GH 7069
        df = hist_df

        fig, axes = mpl.pyplot.subplots(2, 3)
        returned = df.hist(by="classroom", ax=axes[1])
        _check_axes_shape(returned, axes_num=3, layout=(1, 3))
        tm.assert_numpy_array_equal(returned, axes[1])
        assert returned[0].figure is fig

    def test_grouped_hist_multiple_axes_error(self, hist_df):
        # GH 6970, GH 7069
        df = hist_df
        fig, axes = mpl.pyplot.subplots(2, 3)
        # pass different number of axes from required
        msg = "The number of passed axes must be 1, the same as the output plot"
        with pytest.raises(ValueError, match=msg):
            axes = df.hist(column="height", ax=axes)

    def test_axis_share_x(self, hist_df):
        df = hist_df
        # GH4089
        ax1, ax2 = df.hist(column="height", by=df.gender, sharex=True)

        # share x
        assert get_x_axis(ax1).joined(ax1, ax2)
        assert get_x_axis(ax2).joined(ax1, ax2)

        # don't share y
        assert not get_y_axis(ax1).joined(ax1, ax2)
        assert not get_y_axis(ax2).joined(ax1, ax2)

    def test_axis_share_y(self, hist_df):
        df = hist_df
        ax1, ax2 = df.hist(column="height", by=df.gender, sharey=True)

        # share y
        assert get_y_axis(ax1).joined(ax1, ax2)
        assert get_y_axis(ax2).joined(ax1, ax2)

        # don't share x
        assert not get_x_axis(ax1).joined(ax1, ax2)
        assert not get_x_axis(ax2).joined(ax1, ax2)

    def test_axis_share_xy(self, hist_df):
        df = hist_df
        ax1, ax2 = df.hist(column="height", by=df.gender, sharex=True, sharey=True)

        # share both x and y
        assert get_x_axis(ax1).joined(ax1, ax2)
        assert get_x_axis(ax2).joined(ax1, ax2)

        assert get_y_axis(ax1).joined(ax1, ax2)
        assert get_y_axis(ax2).joined(ax1, ax2)

    @pytest.mark.parametrize(
        "histtype, expected",
        [
            ("bar", True),
            ("barstacked", True),
            ("step", False),
            ("stepfilled", True),
        ],
    )
    def test_histtype_argument(self, histtype, expected):
        # GH23992 Verify functioning of histtype argument
        df = DataFrame(
            np.random.default_rng(2).integers(1, 10, size=(10, 2)), columns=["a", "b"]
        )
        ax = df.hist(by="a", histtype=histtype)
        _check_patches_all_filled(ax, filled=expected)