question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>This definitely sounds like a homework, but I assure you that it's not. You're probably familiar with the <a href="http://en.wikipedia.org/wiki/Risk_%28game%29" rel="nofollow">Risk</a> game. Now, friend of mine rolled 3 aces in one hand. I reckon that probability of such event is</p>
<p>$$C(n,k) = \frac{(n-1+k)!}{(... | 69,785 |
<p>Instead of running a certain balanced latin square twice (if you have <em>m</em> experimental conditions but 2 <em>m</em> subjects), what would be a better approach (to cover twice as many of the possible orderings and get the maximum protection against ordering effects etc.)?</p>
<p>...or in general terms, what is... | 69,786 |
<p>I was wondering if any of you have experience in fitting a Cox model to data with missing covariates. Do you know of any reference addressing the issues associated with Cox regression with missing covariates? I know of the approach using the Expectation Maximization (EM) algorithm, but I want to know if there is a ... | 30,408 |
<p>In R suppose that we have the following code:</p>
<pre><code> require("UsingR") # required for "simple.sim" function below
f= function(n=100,mu=0,sigma=1) {
nos = rnorm(n,mu,sigma)
(mean(nos)-mu)/(sigma/sqrt(n))
}
simulations = simple.sim(100,f,100,5,5)
hist(simulations,breaks=10,prob=TRUE)
... | 35 |
<p>I have 3 independent variables (1-5 Likert Scale) questions and I want to check how well these three can predict/explain my DV (1-5 Likert scale)</p>
<p>The three independent variables are:
1. Quality of information
2. Accessibility of staff
3. Quality of technical advice</p>
<p>My DV is:
Overall evaluation of ser... | 69,787 |
<p>I want to compare the performance of two algorithms. Please suggest me some metrics/methods to compare between the algorithms. Below is given a short description of the output of the algorithms.</p>
<p>Suppose there are 100 products (product1, product2,...,product100) each of which has a true rating (true_rate1,tru... | 892 |
<p>I would like to perform an anova for all the columns in my data set.
I tried this:</p>
<pre><code>aov.ex2 <- aov(base~1*2*3,data=data1)
summary(aov.ex2)
</code></pre>
<p>results in </p>
<pre><code>8 1 4.83E+08 482880306 29.802 7.90E-08 ***
2 1 7.34E+07 73427001 4.532 0.03381 *
7 1 ... | 69,788 |
<p>cty time tl</p>
<p>Argentina 2009_Q4 3</p>
<p>Argentina 2010_Q1 2</p>
<p>Argentina 2010_Q2 7</p>
<p>Argentina 2010_Q3 7</p>
<p>Argentina 2010_Q4 10</p>
<p>Argentina 2011_Q1 7</p>
<p>Argentina 2011_Q2 7</p>
<p>Argentina 2011_Q3 1</p>
<p>Argentina 2011_Q4 7</p>
<p>Argentina 201... | 30,409 |
<p>I'm working on a customer retention project that predicts the probability a customer is still subscribing to our services at time T. Unfortunately, we only have the most recent two years of customer data. Estimating the probability of survival at end of year 1 and 2 using Kaplan-Meier is straight-forward. But now we... | 69,789 |
<p>There are many methods to perform regularization -- $L_0$, $L_1$, and $L_2$ norm based regularization for example. According to <a href="http://www.stanford.edu/~hastie/Papers/friedman08a.pdf" rel="nofollow">Friedman Hastie & Tibsharani</a>, the best regularizer depends on the problem: namely the nature of the t... | 37,747 |
<p>Suppose we have constructed a model of some stochastic system; we are also able to perform Monte Carlo simulations of this system. Now, we have two sets of samples: one from our model and one from the MC-based approach, and we would like to assess the accuracy of our technique. </p>
<p>The first two accuracy measur... | 30,410 |
<p>I'm wondering how to explain the <code>logSigma</code> and its p.value in a censored regression model:</p>
<pre><code>require(cenReg)
data( "Affairs", package = "AER" )
estResult <- censReg( affairs ~ age + yearsmarried + religiousness +
occupation + rating, data = Affairs )
summary(es... | 69,790 |
<p>I have a methodological question, and therefore no sample dataset is attached.</p>
<p>I'm planning to do a propensity score adjusted Cox regression that aims to examine whether a certain drug will reduce the risk of an outcome. The study is observational, comprising 10,000 individuals.</p>
<p>The data set contains... | 69,791 |
<p>I have two random variables, $\alpha_i\sim \text{iid }U(0,1),\;\;i=1,2$ where $U(0,1)$ is the
uniform 0-1 distribution. </p>
<p>Then, these yield a process, say:</p>
<p>$$P(x)=\alpha_1\sin(x)+\alpha_2\cos(x), \;\;\;x\in (0,2\pi)$$</p>
<p>Now, i was wondering whether there is a closed form expression for $F^{-1}(... | 40,744 |
<p>I'm using a STL decomposition to make forecasts in R (using the <code>forecast</code> package), but I'm not sure how to incorporate my regressors into the model.</p>
<p>I'm using the forecast function:</p>
<pre><code>f = forecast(stl(my.data, s.window = 'periodic'), h = 12, method = 'arima')
</code></pre>
<p>The ... | 69,792 |
<p>For example, I was looking at <a href="http://en.wikipedia.org/wiki/10-second_barrier" rel="nofollow">this list of the 93 people</a> who have broken the "10-second-barrier", after reading that sprinter Christophe Lemaitre was the first person of purely European decent to break the barrier, which got me to wonder... | 69,793 |
<p>For a statistics assignment, I've been given a data set (regarding drug prevention) and a few questions. One of the questions is to check whether or not the choice of treatment, treatment A or treatment B, impacts the odds of staying drug-free. We're told to be cautious about possible confounds, like a having histor... | 69,794 |
<p>I am trying to figure out the best way to test my data for differences in R. The data I have look like this:</p>
<pre><code>domain variable lifecycle
162 CSP1 5
162 old Species 10
162 BD 16
162 DBH... | 69,795 |
<p>Since we can not fit ARIMA model when the constant variance assumption is violated, what model can be used to fit univariate time series?</p> | 40,749 |
<p>I am evaluating both non-linear LASSO and SVM for a high-dimensional non-linear dataset. In order to do that I am applying 10-fold cross validation. The training error decreases as usual as the model gets more complex. However, the validation/error test always decreases as well, and no minimum can be found. </p>
<p... | 69,796 |
<p>Are there any formulae for the quantiles of a compound gamma/negative binomial distribution? That is, suppose we have</p>
<p>$$N \sim \text{NegBin}(\alpha, \lambda)$$</p>
<p>and conditional on $N$,</p>
<p>$$Y =
\begin{cases}
0 & \text{if } N = 0 \\
\sum_{i=1}^N X_i & \text{otherwise}
\end{cases}$$</p>
... | 69,797 |
<p>I am a graduate student and have a question regarding generalized estimating equation analysis. When conducting across day analysis with GEE, with variable a on day $x$ predicting variable $b$ on day $x+1$, is it necessary to control for previous day's values for variable $b$, or is this correlation already accounte... | 37,639 |
<p>I am performing repeated ANOVAs in SPSS and came across something I don't understand.</p>
<p>Basically, the main effect of group (I have three groups) is not significant (p = .062), but the LSD <em>post hoc</em> test indicates that one of the pair-wise comparisons is significant (p = .032). </p>
<p>How is that pos... | 69,798 |
<p>A minhash implementation with <a href="http://en.wikipedia.org/wiki/MinHash#Variant_with_many_hash_functions" rel="nofollow">multiple hash functions</a> can easily handle comparisons between sets with a vastly different number of elements because the denominator of the unbiased estimator $k$ is based on the number o... | 40,756 |
<p>I have the following model (which is in this form is not identifiable if the $y$'s are indeed endogenous):</p>
<p>(1) $y_1 = a_0 + a_1y_2 + a_2y_3 + \boldsymbol{Xa} + \boldsymbol{u}$</p>
<p>(2) $y_2 = b_0 + b_1y_1 + b_2y_3 + \boldsymbol{Xb} + \boldsymbol{v}$</p>
<p>(3) $y_3 = c_0 + c_1y_1 + c_2y_2 + \boldsymbol{X... | 30,415 |
<p>I am currently conducting a meta-analysis in which I need to use a mixed treatment comparison method. As I understand it, this method works in the following way:</p>
<p>Say you have a group of studies that make the following set of treatment comparisons:</p>
<ul>
<li>Intervention 1</li>
<li>Intervention 2</li>
<l... | 40,757 |
<p>I have a set of GPS coordinates along with their heading angle. These coordinates are within 15 m of each other and so I can use cartesian math to determine the center, std deviation of coordinates etc. I am then trying to find a subset of GPS coordinates that are "above" or "below" the center coordinate. This works... | 36,253 |
<p>Are there methods available to conduct interval-regression style analysis where a predictor variable is the interval variable and the outcome variable is a dichotomous variable? </p>
<p>To give a bit of background, I would like to plot the relationship between two variables in a dataset where the x axis is a contin... | 69,799 |
<p>I have $n$ observations which I want to cluster based on $p$ features. Those $p$ features are dependent to each other (or correlated). If I use Euclidean distance, the weights of all features would be the same, independent from the correlations between them. But what I want is to decrease the weight of a feature in ... | 69,800 |
<p>I'm new to the <code>cforest</code> package and am trying to create a cforest model to predict a new test set and calculate the model test MSE. My data is split into d.train and d.test. If I use randomForest, the code for predicting and determining the MSE is as follows:</p>
<pre><code>set.seed(1)
rfp.data <- ... | 69,801 |
<p>We know that in simple random sampling without replacement the probability of drawing n units from a population of N units(where ordering is considered) is 1/(N)n or 1/(N n) (where ordering is not considered).</p>
<p>How is this equivalent to drawing units independently one by one and with replacement where each un... | 69,802 |
<p>I cannot seem to figure out how to <code>"identify the final point estimates of theta1 and theta2 and verify that they satisfy the invertibility conditions... [and] identify the final point estimate of delta"</code>. All of these are obviously values in the model
$Y_t=\text{ ...}$</p>
<p>I am given a MINITAB outpu... | 69,803 |
<p>I am trying to fit some variables which are high collinear using nnls(non negative least squared routine) in R. </p>
<p>I have about 1 million observations and 200 highly collinear variables for the coefficients to be found.</p>
<p>My problem is that in the final result, the algorithm seems to select variables tha... | 69,804 |
<p>I'm trying to understand the reason why anova(f1, f2, f3) and anova(f1, f2) gives me different result while anova(f1, f2, f3) and anova(f2, f3) gives me the same.</p>
<p>Here's the code:</p>
<pre><code>> data(swiss)
> fit1 <- lm(Fertility ~ Agriculture, data=swiss)
> fit3 <- lm(Fertility ~ Agricultu... | 18,001 |
<p>The following is a Bayesian model, there are variables $Y_1,Y_2 \in \{ 0,1 \}$ and variable $X \in \{ 0, 1\}$ and $\theta$ between $0$ and $1$.</p>
<p>The model is:</p>
<ol>
<li>draw $\theta$ from Beta distribution with parameters $a$ and $b$</li>
<li>draw $Y_1$ from Bernoulli $\theta$</li>
<li>draw $Y_2$ from Ber... | 69,805 |
<ol>
<li>The problem statement, all variables and given/known data</li>
</ol>
<p>I am given a set of x and y values x: (1,2,3,etc.) y: (1.2,2.2,3.1,etc.) with a given uncertainty and am asked</p>
<p>a) find the best fit </p>
<p>b) at what prob can you rule out a 5% higher slope</p>
<p>c) is the stated uncertainty c... | 69,806 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/34587/determining-a-correction-factor-and-applying-it-to-a-second-set-of-numbers">Determining a correction factor and applying it to a second set of numbers</a> </p>
</blockquote>
<p>1st- I would like to f... | 49,836 |
<p>So here's the situation:
There are n balls. Each ball has been voted on a scale of 1-N by an arbitrary number of people.</p>
<p>Every day (or every week, or more), some/most/all of the previous voters and some new voters are able to vote on the balls again. The thing is, I don't want all previous votes to all disap... | 69,807 |
<p>A <a href="http://en.wikipedia.org/wiki/Variogram" rel="nofollow">variogram</a> plots the variance of the difference between sample pairs on a field (any dimensionality) against spatial separation (the "lag") of those samples.</p>
<p>The extrapolation from observed small-lag variances to a zero-lag variogram value ... | 30,423 |
<p>My data has 3 major inputs: <code>BLDDAY</code> (a factor), <code>BLDMNT</code> (a factor), and <code>D_BLD_SER</code> (days as an integer variable). The output is whether input variable has any impact on failure. My model is: <code>model = glm(FAILED~BLDDAY+BLDMNT+D_BLD_SER, family="binomial", data=data_list)</co... | 18,002 |
<p>I may have a tricky question. I have a within design where every participant is tested in 2 conditions. I want to compare the dispersion of the measure, for the two condition, with the hypotheses that one condition has a larger dispersion than the other one. I though about taking the sd to get a measure of dispersio... | 69,808 |
<p>I am struggling with a proof, and I am wondering if anyone can help or point me to the right direction. Suppose that we have two variables, $X$ and $Y$, and they follow a multivariate normal distribution with covariance matrix $Q$. Now, suppose that we have two more variables, $Z_1$ and $Z_2$ that follow a normal di... | 69,809 |
<p>I am trying to learn various cross validation methods, primarily with intention to apply to supervised multivariate analysis techniques. Two I have come across are K-fold and Monte Carlo cross-validation techniques. I have read that K-fold is a variation on Monte Carlo but I'm not sure I fully understand what makes ... | 69,810 |
<p>Today I tried to estimate models using both <code>plm</code> and <code>pgmm</code> functions in the <a href="http://cran.r-project.org/web/packages/plm/index.html" rel="nofollow">plm</a> R package, with an interaction between <code>X1</code> and <code>lag(X2, 1)</code>. And I notice two issues.</p>
<p>Let $Y=b_1 X... | 38,601 |
<p>Suppose I use K-S to figure out if the CDF of $X$ is greater than the CDF of $Y$. I get the statistic $D^+ = \max_u\{C_x(u) - C_y(u)\}$ where $C_x$ is the ECDF for $X$ and similarly for $C_y$.</p>
<p>There are various tables which translate this into a p-value. Intuitively, if I'm testing if $C_x < C_y$ it seems... | 40,142 |
<p>I'm performing a multiple logistic regression with a large amount of columns. I want to set all the variables over a certain p value to have 0 coefficients, then test the model on the test data. </p>
<p>Since there's so many variables I'm using, it's impractical to manually go in and set the coefficients. So I'm lo... | 30,429 |
<p><strong>Preliminaries</strong></p>
<p>For simplicity's sake assume we are dealing with a 2-dimensional dataset of examples $(x_i, y_i) \in \mathbb{R}^2$ which are split into a training (objects and their label known) and test set (only objects known). </p>
<p>Prediction using <em>least squares</em> can be repr... | 69,811 |
<p>I have a data set, whose elements (say 1,000 elements) are numeric with values between 0 and 1. It is safe to think the elements are independent from each other, i.e, the order of these elements does not matter at all. Also, from the histogram of the data set, I can tell it does not follow any parametric distributio... | 37,643 |
<p>Imagine $N$ baskets each filled with a different number of products chosen from a set $P$. It is possible to have repeated products in the same basket.</p>
<p>For instance:</p>
<pre><code>basket 1 = [A,B,B,C]
basket 2 = [A,B,C,D,F,J]
basket 3 = [C]
...
basket N = [E,E,E,F,F]
</code></pre>
<p>Now we ask someone to... | 69,812 |
<p>I have a matrix which I'm trying to run through the <code>mirt</code> function of the <code>mirt</code> package:</p>
<pre><code>resp.freq <- data.frame(matrix(c(11, 46, 12, 31, 13, 8, 21, 20, 22, 68, 23, 12,
31, 1, 32, 12, 33, 11), nrow = 9, ncol = 2,
... | 69,813 |
<p>I have a very basic question on clustering. After I have found k clusters with their centroids, how do I go about interpreting the classes of the data points that I have clustered (assigning meaningful class labels to each cluster). I am not talking about validation of the clusters found.</p>
<p>Can it be done give... | 49,705 |
<p>I am running a SEM on lavaan in R.</p>
<p>The model consists of latent variables [N1 to N3], two dummy choice variables [du1 and du2] and observed satisfaction variable [SV] (beside the observed variables).</p>
<p>Without the dummy choice variables, this is visually what the model should look like (without interce... | 30,431 |
<p>In a longitudinal study, two groups of subjects have been measured over a period of two years at 6 months intervals. During these measurements subjects have been assessed with a series of $k$ measures ($M_1$ to $M_k$). </p>
<p>From other sources we expect to see a difference between the groups and a decline in the ... | 40,780 |
<p>I'm still learning about deep learning. However I'm currently interested to know if deep learning architectures scale well or not. Suppose I have a dataset with 1 million training examples, can you give me some rough estimates how much time would it take to train a deep architecture on such a dataset? I know there a... | 69,814 |
<p>I'm trying to estimate quantiles from cumulative distribution functions. Given N CDFs are there techniques that can be used to merge them to form another CDF from which a quantile can be estimated ? </p>
<p>Thanks everyone for looking at the question. Here is a more concrete example: Imagine a web service being s... | 69,815 |
<p>I have a numeric dataset and I would like to apply classification algorithms on it. So I am using Weka's Discretize filter to convert the numeric values to discrete. However I wonder what can be the implications of converting all the attributes (including the class label) to discrete vs. converting only the class la... | 69,816 |
<p>Given the following two time series (<strong>x</strong>, <strong>y</strong>; see below), what is the best method to model the relationship between the long-term trends in this data? </p>
<p>Both time series have significant Durbin-Watson tests when modelled as a function of time and neither are stationary (as I un... | 37,644 |
<p>
I'm trying to make sense of the multivariate case of the Cramér-Rao inequality. One of its conditions of regularity <a href="http://en.wikipedia.org/w/index.php?title=Cram%C3%A9r%E2%80%93Rao_bound&oldid=557409775#Regularity_conditions" rel="nofollow">states</a>:
<blockquote>
$$
\frac{\partial}{\partial\theta}\left... | 69,817 |
<p>I have two time series that I am investigating, acc and amb, the time frequency is daily data. They are both non stationary, as evidenced by the follows:</p>
<pre><code>adf.test(df$acc)
Augmented Dickey-Fuller Test
data: df$acc
Dickey-Fuller = -2.7741, Lag order = 5, p-value = 0.2519
alternative hypothesis: ... | 69,818 |
<p>I have a data set used in a regression with 30 attributes and 30K instances. I am trying out a bunch of algorithms (SMO regression, Linear Regression and K-NN) but it was quite surprising to see that K-NN performs much better than SMO and Linear Regression.</p>
<p>Since K-NN is a very naive algorithm compared with ... | 30,434 |
<p>I am trying to interpret my interaction effects, which are all negative.
One example:
Experience (variable A) x absolute size of the acquired knowledge base (variable B): B= -0.002, exp(B)= 0.998.</p>
<p>Can I interpret this interaction in the following way: As variable B decreases, the effect of A increases.
How c... | 30,435 |
<p>I had a project from before I graduated from college that was effectively me acting as a research aid to a politician. The project served as my senior thesis, as well. The portion of the report that I was working on focused on determining the effect of new fuel economy legislation for heavy-duty vehicles, such as 18... | 69,819 |
<p>The ELO rating system and later improvements like Glicko are specifically designed, as far as I know, for mirror games. That is, we assume that no player has a systematic advantage over another. In chess, this is typically the case because a player will be black/white a roughly equal number of times. </p>
<p>But... | 40,786 |
<p>I am conducting a study, in which I will be using Logistic Regression for analysis. I will be collecting data in an education setting (about cancer prevention), then I will follow subjects to collect data on who took action after their education (cancer prevention screening) among those who were educated. The two gr... | 40,788 |
<p>I keep reading about instances where we center the data (e.g., with regularization or PCA) in order to remove the intercept (as mentioned in <a href="http://stats.stackexchange.com/questions/19523/need-for-centering-and-standardizing-data-in-regression">this question</a>). I know it's simple, but I'm having a hard t... | 49,406 |
<p>I was wondering if anyone could give me some insight on the relation between the ACF and the periodogram of a time series.</p>
<p>I have a bunch of timeseries and their ACF's and periodograms are typically much like the examples below.</p>
<p>For my analysis, I'm mostly interested in periodicity at lag 8 and 16 (f... | 30,441 |
<p>I have a model which includes the following priors:</p>
<p>$\lambda_C \rightarrow \dfrac{1}{\sigma_C^2}$</p>
<p>and</p>
<p>$\sigma \sim \text{uniform}(0,500)$</p>
<p>Where $\sigma$ is the standard deviation and $\lambda_C$ is the precision of a normal distribution.</p>
<p>Being a beginner, I have problems conce... | 69,820 |
<p>Let:
population size $=N$;
sample size $=n$;
sampling interval $=\frac{N}{n} = k$, which can be non-integer; and
$r=$ random starting point, which can be non-integer, $0 < r < k$.</p>
<p><a href="http://en.wikipedia.org/wiki/Systematic_sampling" rel="nofollow">http://en.wikipedia.org/wiki/Systematic_sampling<... | 30,442 |
<p>When measuring predictive performance of a regression model, I am thinking about using repeated data splitting (or leave-out data at random) instead of using bootstrapping.</p>
<p>By "repeated data splitting" (not sure if that's even term) I understand:</p>
<pre><code>FOR N=10000
Sample 70% of the data points and ... | 69,821 |
<p>I have a dataset of point coordinates of individuals and different variables of these individuals. I want to calculate if the spatial distribution of a certain variable is correlated to the spatial distribution of a different variable. For example: do patches of large plants have higher predation rates, even small p... | 69,822 |
<p>I am building a predictive model that forecasts a student's probability of success at the end of a term. I’m specifically interested in whether the student succeeds or fails, where success is usually defined as completing the course and achieving 70% or more points out of the total points possible.</p>
<p>When I de... | 37,482 |
<p>There are various definitions of fixed and random effects in linear mixed-effects models in the statistics literature, and even in the fixed-effects models from econometrics. The data I have now represent the entire consumption of some products in a country. I aggregated them to annual level for 6 years by each stat... | 30,447 |
<p>I have got a dataset:</p>
<blockquote>
<p>The attribute of interest: Count. I work out the linear model of
Count, then the root mean square error (<code>gmdl.rmse</code>). </p>
<p><code>buffer1</code> and <code>buffer2</code> of length <code>w</code>. In this case <code>w=3</code>. Therefore
<code>buffer... | 69,823 |
<p>In <code>R</code>, given a set of numerical data, how do I decide the top 1% of these data, and replace them with a new value, say, e.g. $10^{10}$ </p> | 69,824 |
<p>There is a <a href="http://stats.stackexchange.com/questions/23224/cohens-d-for-2x2-interaction">nice answer</a> to this question, but it assumes that you have the ANOVA table available.</p>
<p>My problem is different. Say I'm reading a paper describing a male vs female, disease vs control experiment, and I know t... | 69,825 |
<p>I am trying to compare the performance of a classification result with Bayes classifier, K-NN, principal component analysis (PCA). </p>
<p>I have doubts regarding the following (please excuse my lack of programming skills since I am a biologist and not a programmer thus finding hard to follow the matlab documentati... | 69,826 |
<p><strong>EP Primal</strong> </p>
<p>In <a href="http://research.microsoft.com/en-us/um/people/minka/papers/ep/minka-ep-energy.pdf" rel="nofollow">1</a>, it is finding the EP iterations by solving a saddle-point problem on the energy function. First, the primal is claimed to be
$$
\min_{\hat{p}_i} \max_{q} \left[ ... | 69,827 |
<p>I recently read a post from R-Bloggers, that linked to <a href="http://www.johnmyleswhite.com/notebook/2012/03/31/julia-i-love-you/">this blog post</a> from John Myles White about a new language called <a href="http://julialang.org/">Julia</a>. Julia takes advantage of a just-in-time compiler that gives it wicked fa... | 37,545 |
<p>I'm totally not a pro in statistics so i hope the question is not too simple!</p>
<p>I have two groups of patients. One group are smokers, the second are non-smokers.</p>
<p>I want to compare the level of some hormones in the two groups to see if they are influenced by smoking. On many articles I found researcher... | 49,522 |
<p>Are there any open source software packages, (Java, Matlab, R) that can generate a feature representation for a text document using N-gram model? </p> | 40,793 |
<p>I have registry data for which I have data for individuals for each hospital attendance over a 10 year period. I wish to determine the effect of chronic antibiotic use upon acquisition of specific infections (outcome). However, often the choice of antibiotic may differ over time and so I want to be able to summari... | 69,828 |
<p>I am very new in PLS and I try to understand the output of the R function plsr(). Let us simulate data and run the PLS:</p>
<pre><code>library(pls)
n <- 50
x1 <- rnorm(n); xx1 <- scale(x1)
x2 <- rnorm(n); xx2 <- scale(x2)
y <- x1 + x2 + rnorm(n,0,0.1); yy <- scale(y)
p <- plsr(yy ~ xx1+xx2,... | 40,798 |
<p>One of the important OLS assumptions is a strict exogeneity assumption, i.e. $E(\epsilon_i | X) = 0, \forall i$. I'm interested in testing empirically this hypothesis, notably in the context of time series.</p>
<p>It is known that exogeneity is rarely true in time series but assuming that the model is well specifie... | 69,829 |
<p>Hi there I am running a k-means code in R with the same data and with the same number of clusters, in this case 3, but each time that I run the code, the cluster label changes, for example. </p>
<p>In the first run I got this results </p>
<p>Col A Cluster.K-means</p>
<p>FirstOBS Cluster1,</p>
<p>SecondOBS Clust... | 69,830 |
<p>I was studying on a PAMI article and I have seen an equation like this:</p>
<p>$$
\begin{align*}
P(B|X) &= \prod_c{P(B^c|X)} \\
&= \prod_c{P(B^c|A^c)}
\end{align*}
$$</p>
<p>where $A^c$ is a function of $X$.</p>
<p>I know to fully understand the derivation details are needed, but what I am wonderi... | 40,800 |
<p>I was running PLS regression on the data which is weighted and gives the following error message: </p>
<pre><code>Error: The dataset is weighted, but this procedure cannot be used with weights
</code></pre>
<p>I do not understand the reason for this as earlier with weights on, there was an outcome.</p> | 40,802 |
<p>I have an estimated population size for which individual covariates are known for only a smaller sample of the population. So for example, my total population size is estimated to be 26.9 individuals/ha, SE = 4.4, lcl = 19.6, ucl = 36.9. I know that the population is 30% male, and 70% female (from a smaller sample o... | 69,831 |
<p>Lets' say I have a Poisson distribution for which I use a <em>maximum likelihood</em> defined as:</p>
<p>$P_i=\frac{m_i^{n_i}}{e^{m_i}n_i!}$</p>
<p>where $m_i$ represents the <strong>model</strong> value of bin $i$ (real, $m_i$> 0) and $n_i$ its <strong>observed</strong> value (integer, number of counts in bin $i$... | 69,832 |
<p>I'm a Physics student and we had a lab where we had to process some data in the form $x_i$, $y_i$, $\sigma_i$, where the $\sigma_i$'s are the uncertainties of the $y_i$'s.</p>
<p>With the weighted least squares method we obtained coefficients $A$ and $B$, the estimated parameters for a straight line in the form $y ... | 69,833 |
<p>I am trying to build a model to explain an ordinal response variable $y$ with 4 levels: $y_0$, $y_1$, $y_2$ and $y_3$. The independent variable in this model is $v$. $v$ is a categorical variable with three categories $v_a$, $v_b$ and $v_c$. The assumption of proportional odds fails for $v$. Therefore, I am using t... | 40,805 |
<p>In the text mining, besides N-gram model, what are the state-of-art models for building feature space while capturing the dependence among the different words, or capturing the semantic meaning in the article?</p> | 40,806 |
<p>I'm using the <code>logistf</code> package in R to perform Firth logistic regression on an unbalanced dataset. I have a logistf object:</p>
<pre><code>fit = logistf(a~b)
</code></pre>
<p>Is there a <code>predict()</code> function like on that's used in the <code>lm</code> class to predict probabilities for future ... | 69,834 |
<p>Is there such a thing as a fair die? On dice where the number is represented by a scooped out dot, surely that makes a difference? Has anyone done any research?</p>
<p>In fact thinking about it, why would a coin flip be fair? the physics on each side is completely different.</p> | 40,808 |
<p>I have a set of data that looks at the number of "hits" a specific program makes over the course of time. The data goes back to September 2010, and includes data up to March 2011, so the data points are monthly. What I want to see if the most recent data (March 2011) shows a statistically significant decrease in t... | 69,835 |
<p>I have a <strong>Machine Learning</strong> course this semester and the professor asked us to find a <strong>real-world problem</strong> and solve it by one of machine learning methods introduced in the class, as:</p>
<ul>
<li><a href="http://en.wikipedia.org/wiki/Decision_tree_learning">Decision Trees</a></li>
<li... | 69,836 |
<h3>Question on pairs()</h3>
<p>I'd like to use <code>pairs()</code> to choose a functional form for modeling a set of data. I know that several of my independent and dependent variables are probably lognormally distributed, so I'd like to produce <code>pairs()</code> plots where some of my variables are plotted on l... | 30,468 |
<p>I'd like to model a set of processes. The processes in question are related to human-decision making, so the model will need a measure of input, processing, and then, finally, output.
Ideally, the model would be implemented in something like R (which I know quite well) or Python (which I know less well). </p>
<h3>Q... | 69,837 |
<p>Is it incorrect terminology to say that data follows a t-distribution random walk, for example? Does the fact the increments have this underlying distribution mean it should be referred to as a markov chain (and random walk is just a type of mc with a uniform distribution of increments)?</p> | 69,838 |
<p>I am trying to perform cluster analysis on survey data where each respondent has answered several questions, some of which have categorical answers ("blue" "pink" "green" etc) and some of which have scale answers (rating from 1 to 10 etc).</p>
<p>My problem is that certain age groups were over-sampled and I need to... | 1,809 |
<p>I am working on a problem that has can beyond my level of understanding. I am quite familiar with R, so that would be my preferred choice but I also have access to SAS.</p>
<p><strong>Data</strong></p>
<p>I have created a fake dataset with a couple of rows <a href="https://docs.google.com/spreadsheets/d/1mAyKRV24m... | 69,839 |
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