question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I have a large dataset of 30,000 cases with 150 variables. I am looking for a few possible machine learning solutions/methods that I could try and use for cross validation. </p>
<p>My dependent variable is a percent/continuous variable while all my independent variables are continuous or discrete categorical vari... | 71,592 |
<p>I have a very lengthy but poorly designed questionnaire, which has a very large number of questions. The questionnaire really needs to be completely rewritten, but prior to that being done, there is an organisational need to use it again in the short term.</p>
<p>Given the length of the questionnaire, it would be ... | 351 |
<p>I have a set of numbers generated from Gamma distribution. How can I verify that these values were all randomly generated from Gamma or satisfy Gamma distribution?</p> | 71,593 |
<p>I am new to multimodel inference. I am trying to create a model that has multiple categorical factors and possible interactions. For example say that my model is...</p>
<blockquote>
<p>Y ~ X1 + factor(X2) + factor(X3)</p>
</blockquote>
<p>say each factor has two possible categories. R is only giving me AIC in my... | 71,594 |
<p>It's not clear how to build models when using the Stata <code>gb2lfit</code> module. Output includes two tables, parameter estimates and their logs. The significance tests can sometimes differ between the tables, with the paramter estimates being significant and the logs not. On which table ahould decisions about... | 71,595 |
<p>L1 penalized regression introduces a bias on your regression model but decreases the variance. When this bias is introduced, is it possible that the coefficient of $B$ changes sign? This would greatly affect the interpretation, where a regular regression might tell you an increase in $x$ increases $y$ by $B$, but ... | 44,071 |
<p>On visual inspection of P-P plots, my time data appears to fit a Weibull distribution better than a normal distribution. I will use the variable for correlations and as a predictor in regression. In SPSS, I could fit the data to a Weibull regression model. I have also read that you can Vincentize the data, but I am ... | 11,681 |
<p>I have two arrangements(i.e. permutations) of numbers. First one is the target/real arrangement. Second, is the observed arrangement.</p>
<blockquote>
<p>e.g.</p>
<p>Target := 1,2,3,4,5,6,7</p>
<p>Observed := 4,1,7,3,2,5,6</p>
</blockquote>
<p>Any two elements in an arrangement is not equal. What kind ... | 33,142 |
<p>I'm using a Gibbs sampler for Latent Dirichlet allocation as described by Griffiths and Steyvers (<a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC387300/" rel="nofollow">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC387300/</a>). The sampling of a new topic $j$ for word $i$ is described by</p>
<p>$P(z_i = j | \... | 71,596 |
<p>I'm trying to test the significance of the "component" effect in a multivariate regression model. I'm not sure what is the right way. Using R, I have tried a way with <code>lm()</code> and another way with <code>gls()</code>, and they don't yield compatible results. </p>
<p><strong>Please note that this is not a qu... | 71,597 |
<p>Suppose that I have $n$ independent samples from a probability distribution. I believe that the distribution is Gaussian ($G$) but I don't know; then my question is: does there exist a test such that I can interpret the result of the test to be something like "the probability that my samples are the output of a non-... | 71,598 |
<p>In general, what the the standard hypothesis tests in all types of regression? We get some coefficients and then test the hypotheses that these coefficients are significant (i.e not equal to $0$)? For example, in logistic regression the p-value indicates that the regression coefficients are significant or not? Likew... | 71,599 |
<p>I have 1000 uniformly distributed random numbers. How do I manipulate them to get a V-shaped histogram?</p> | 71,600 |
<p>I have a time series of assets ${A_1, A_2, ..., A_n}$, which is described by a sophisticated distribution having the following characteristic function: $\phi(u; t;\theta)$, where $\theta$ is a vector of unknown parameters.
I need to esimate vector of unknown parameters $\theta$ of characteristic function. </p>
<p... | 71,601 |
<p>I have some data in which there are 5 categorical explanatory variables (<code>concern, breath, weath, sleep, act</code>) and 1 continuous response variable (<code>tto</code>). In addition, every categorical explanatory variable is divided into 5 levels which show how strong a person feels about it. level 1 and leve... | 711 |
<p>I have a large simulated loss data (from catastrophic models developed at my school) to calculate some extreme quantiles. Previously they used non-parametric methods to do this (find the point estimate for these extreme quantiles and CIs). </p>
<p>I am using parametric models (extreme value theory, fat tail distrib... | 16,792 |
<p>I have trouble understanding KL divergence, where P is probability mass function of true distribution of data and Q is the approximation of P. </p>
<p>The definition of KL divergence is: </p>
<p>$$D_{\mathrm{kl}}(P || Q) = \sum_i \ln\left( \frac{P_i}{Q_i}\right)P_i$$</p>
<p>If I want a symmetrised KL divergence, ... | 33,150 |
<p>Can someone please explain why when I do an ARIMA model the forecast's 95% confidence interval widen?</p> | 71,602 |
<p>I am writing a paper about Algo-trading and my supervisor asked me to test the hypothesis that "the return of the trading strategy is significantly different than the average".</p>
<p>To reach this result, it has been implemented a software doing the following:</p>
<ol>
<li>Compute the profit by trading on a certa... | 33,151 |
<p>I have what seems like a textbook binary hypothesis testing scenario: an observation $X$ drawn from one of two probability distributions $\{\Pi_0,\Pi_1\}$ that are known to me, and a need to classify $X$ as having been drawn either according to $\Pi_0$ or $\Pi_1$ (without loss of generality, let's assume equal prior... | 71,603 |
<p>H0: Male and Female members do not differ in average Awareness, Attitude and Loyalty
Ha: Male and Female members differ in average Awareness, Attitude and Loyalty. </p>
<p>STEP 1: Used a Levene's Test to find for equal variances
According to the Levene's test - P value across all variables from the Levene’s test of... | 71,604 |
<p><em>I received the following question via email and thought it would be suited to this site:</em> </p>
<blockquote>
<p>I have a debate with a friend about factor loading and squared
multiple correlation. ...
In my debate with my colleague, I argue that regression weights/factor
loading above 0.6 is enough ... | 71,605 |
<p>So we're starting to do A/B testing in my company (it's a mobile app), and my CEO is pretty skeptical about the whole thing (I guess I can't blame him, especially after the results I'm seeing).</p>
<p>One of our first tests is to delay showing ads for 1 day vs. 2 days. The "control" in this case is 2 days, which is... | 71,606 |
<p>I am new to forecasting.</p>
<p>I have weekly data. </p>
<p>I want to forecast using the Holt-Winters method.</p>
<p>Should I make training and test subsets of the data? </p>
<p>How important are the training and test data?</p> | 30,652 |
<p>The query I have relates to calculating the variance of AR(1) processes that are smoothed with a simple moving average. So:</p>
<p>In an AR(1) process of the form:</p>
<p>$$ X_t=c+\varphi X_{t-1}+\varepsilon_t, $$</p>
<p>the variance can be calculated as:</p>
<p>$$ \text{var}(X_t)=E(X^2_t)-\mu^2=\frac{\sigma^2_{... | 33,157 |
<p>I'm wondering what the value is in taking a continuous predictor variable and breaking it up (e.g., into quintiles), before using it in a model. </p>
<p>It seems to me that by binning the variable we lose information.</p>
<ul>
<li>Is this just so we can model non-linear effects? </li>
<li>If we kept the variable c... | 49,907 |
<p>I am not very familiar with mixed models --- I have been reviewing the various tutorials on the web but still am not sure how to specify my model, even as a starting point for comparison. I have a relatively simple design:</p>
<ul>
<li>two non-random groups (normal/obese) -- randomized within each group to two cond... | 71,607 |
<p>In logistic regression with an N of 40,000, purchase decision is unrelated to price. However, with certain demographic variables controlled, price can show a positive coefficient of meaningful strength. (Searches for 2-, 3-, and 4-way interactions involving price have yielded nothing.) </p>
<p>The goal here is to... | 33,159 |
<p>I am not sure in the terminology, so I will simply try to explain the situation that I would like to model as I see it. Suppose there is a set of random variables. The variables are correlated in such a way that they deviate from their expected values into the same direction all together. By this I mean that they ca... | 33,160 |
<p>Can someone explain my Cox model to me in plain English? </p>
<p>I fitted the following Cox regression model to <strong>all</strong> of my data using the <code>cph</code> function. My data are saved in an object called <code>Data</code>. The variables <code>w</code>, <code>x</code>, and <code>y</code> are continuou... | 71,608 |
<p>For any particular nonlinear regression: $$Y_i = f(\mathbb{x_i},\theta) + \epsilon_i, i=1,...,n$$ I currently have standard errors for each of the $\theta_j$ obtained via the Gauss-Newton algorithm</p>
<p>Is there a systematic relationship between these standard errors and the sample size such that I would be able ... | 71,609 |
<p>I'm running an analysis on a few data sets that each typically have 100-200 cases measured across 120-160 variables - something similar to looking at gene expressions. Each variable is a non-centered score for expression of a particular attribute frequency for each case. In many cases though, any given attribute is ... | 33,164 |
<p>I'm trying to determine if the exponential distribution is a good model for a data set that I'm exploring. It doesn't have to be precise. I'm using the data for capacity planning (if it's a good fit) and for my own learning. I found a data set that I have ready access to and I wanted to test to see it fit a known di... | 44,100 |
<p>For an OLS model the mean squared error can be used to assess the fit of the trained model on the validation data.</p>
<p>What is the equivalent for a logistic regression model? Can I simply use the following residual sum of squares function?</p>
<p>$RSS=\Sigma^N_{i=1}(y_i-{\hat p})^2$</p> | 33,165 |
<p>I am trying to compute eigenvalues in C++ using the <code>Armadillo</code> function <code>eig_sym</code> via RcppArmadillo. The results are not entirely the same as the output of the R function <code>eigen()</code>:</p>
<p>In R:</p>
<pre><code>set.seed(1)
X=matrix(sample(1:25), 5)
X
# [,1] [,2] [,3] [,4] [,5]... | 71,610 |
<p>I'm trying to fit a simple exponential model for left censored data using RSTAN to replicate something I did in JAGS. </p>
<p>The JAGS model is:</p>
<pre><code>model{
for(i in 1:N){
isAboveLOD[i] ~ dinterval(x[i], LOD[i])
x[i] ~ dexp(lambda)
}
lambda ~ dgamma(0.001, 0.001)
}
</code></pre>
<p>A full... | 33,166 |
<p>Assume I have 1000 samples of data. I split the data randomly into training and test sets of size 800 and 200, respectively. Now, I train a classifier using the training set, and then evaluate the performance of the classifier using the test set. Assume I am not satisfied with the results. So, I change some paramete... | 71,611 |
<p>The <code>effect-size</code> tag has no wiki. The <a href="http://en.wikipedia.org/wiki/Effect_size">wikipedia page about the effect size</a> does not provide a precise general definition. And I have never seen a general definition of the <em>effect size</em>. However when reading some discussions such as <a href="h... | 71,612 |
<p>Suppose you have some multivariate normal distribution $X \sim N(\mu,\Sigma)$. Is there a good way to calculate a measure of distance between an arbitrary $X_{i}$ and $X_{j}$ of $X$ (I suppose the simplest approach would be to begin with a two dimensional distribution, which can be obtained through the conditional m... | 44,104 |
<p>Let's assume one has looked at the occurence of a plant species at different altitude, different temperature and environment. Here are its data:</p>
<pre><code> Temperature environment altitude
plant1 18.1 mud 812
plant2 15.3 field 754
p... | 71,613 |
<p>I have a dataset looking like:</p>
<pre><code>> dat
time censoring x
1 20 0 NA
2 10 0 NA
3 60 0 NA
4 80 0 NA
5 100 1 5
6 10 0 NA
7 100 1 6
</code></pre>
<p>(Of course the real dataset is bigger). The "time" column is the time-to-death of t... | 71,614 |
<p>I have two different sources for order / purchase related data, one is at individual (purchase) level, the other is aggregated daily. Both sources contain different <em>types</em> of data points, albeit all related to purchases. I want to use this data to model changes in purchase patterns. My question is can I use ... | 44,108 |
<p>I want to model two different time variables, some of which are heavily collinear in my data (age + cohort = period). Doing this I ran into some trouble with <code>lmer</code> and and interactions of <code>poly()</code>, but it's probably not limited to <code>lmer</code>, I got the same results with <code>nlme</code... | 37,876 |
<p>I'm working on highly skewed data, so I'm using the median instead of the mean to summarise the central tendency. I'd like to have a measure of dispersion
While I often see people reporting <strong>mean $\pm$ standard deviation</strong> or <strong>median$\pm$quartiles</strong> to summarise the central tendency, is ... | 33,172 |
<p>i suppose one way to characterize data is by a combination of the variable types that comprises it:</p>
<pre><code> Continuous/Continuous | Continuous/Discrete
-----------------------|---------------------
Discrete/Discrete | Discrete/Continuous
</code></pre>
<p>Each of the four cells comprising the 2x2 ... | 71,615 |
<p>If I have daily data set and it's a non-stationary series, then what is the lag I have to consider for the first difference 1 or 7?</p> | 33,173 |
<p>It is my task to program a mixed model. The data is from 20 experimental subjects, who were measured under 2 factors. Factor A has 7 levels, factor B has 3 levels. So, that for every subject I got 21 data points. The data points for one subject are repeated. I analysed the data with repeated measurement ANOVA just t... | 71,616 |
<p>I have read about <a href="https://www.google.com/search?q=%22geometric%20random%20walk%22#q=%22arithmetic%20random%20walk%22" rel="nofollow">arithmetic</a> and <a href="https://www.google.com/search?q=%22geometric%20random%20walk%22" rel="nofollow">geometric</a> random walks. What is the difference between them?</p... | 71,617 |
<p>Is there a good, modern treatment covering the various methods of multivariate interpolation, including which methodologies are typically best for particular types of problems? I'm interested in a solid statistical treatment including error estimates under various model assumptions.</p>
<p>An example:</p>
<p><a hr... | 71,618 |
<p>I saw in the book of Rubin (1987) that an increase in variance of estimation will occur due to nonresponses. But I wonder the reason behind this. Thanks for your shares!</p> | 33,176 |
<p>I have been looking at ways to carry out unsupervised clustering of data with both numeric and nominal (but not ordinal) variables. I also suspect non-linearity in the data.</p>
<p>A possible solution would appear to be as follows: (1) use Random Forest in unsupervised mode to get a matrix of pairwise similarities ... | 71,619 |
<p>Consider that $\theta$ is an hidden parameter and one has an observation such that $O$:
$$
O \sim N(\theta,\sigma^2).
$$
My question concerning vocabulary: </p>
<p>do we measure $\theta$ and it gives us $O$? (so we measure the true value)</p>
<p>or </p>
<p>do we measure $O$ ? (so we measure the observation)</p>
... | 33,179 |
<p>In karlin-Rubin theorem, after showing that power function is an increasing function, we take hypothesis H0: Theta=Theta0 vs H1: Theta=Theta1. then how do they show that
{sup(thet<= theta0) power function} is = alpha?</p>
<p>I am not able to understand this from any of the research paper.</p> | 71,620 |
<p>i get that you have to find the roots of the characteristic polynomial but can someone explain the intuition behind the roots must be outside the unit circle? what is a unit circle? </p>
<p>before anyone downvotes me saying theres another similar discussion, i have read it and i dont understand what it means for ro... | 44,715 |
<p>Using longitudinal survey data on children using psychotropic medications, we are interested in estimating associations with medication classes, their persistence and adherence (longitudinal exposures), and certain rare outcomes such as suicidal idealization. There are clusters defined at the child level with no clu... | 71,621 |
<p>I have 10,000 documents. Each document has a label ($Y$) that is either $0$ or $1$ (the 0-1 split is pretty much 50/50 over my 10,000 documents). Each document has 10 fields. Each field can have any number of words in it. I create 10 feature-spaces by fitting a tf-idf over each field individually over all documents.... | 71,622 |
<p>I have two questions on interpreting the statistical analysis of data collected from production runs to produce an experimental material. We made four production runs, with some changes in each run. Each run produced three pieces of material, and each piece of material was tested in multiple places to measure the p... | 33,184 |
<p>Ex. series, say stock prices
103 101 102 <strong>150</strong> 101 102 100
First differenced
2 1 <strong>48</strong> <strong>-49</strong> 1 -2
Notice you could guess a very large negative number following the very large positive in the first differenced numbers.</p>
<p>Is it the case that negative serial cor... | 71,623 |
<p>I need your advice to know how to restore certain market maker algorithm based on historical data.</p>
<p>I have dataset with limit order book information at discrete time periods. For every time moment it contains best bid/ask prices and volume of fist 10 asks and 10 bids. Also it has bid and ask prices - the choi... | 71,624 |
<p>I have $10^8$ vectors in $1000$ dimensions each. I would like to drastically reduce their dimensions. However PCA seems computationally infeasible. Are there near linear time methods to do dimensionality reduction?</p> | 71,625 |
<p>I have some data where I have certain classes (c1, c2, c3, c4 ...) and the data comprises of binary vectors where 1 and 0 denote that an entry belongs to a class or not. The number of classes will be > 200. The data will look like this:</p>
<pre><code>c1 c2 c3 c4 ...
1 0 0 0 ...
0 1... | 71,626 |
<p>I sampled some data at certain sampling rate (e.g., 1 sample per minute). I want to know whether the values in this data set are continuously growing or they are just fluctuating around certain value. How can I do that?</p>
<p>In addition, I would like to predict the future values to be sampled. Based on the predic... | 44,120 |
<p>I have a data set that looks like this:</p>
<pre><code>GROUP WEEK1 WEIGHT(kg) WEEK2 WEIGHT(kg) WEEK3 WEIGHT(kg)
Control
Subject C1 40 42 44
Subject C2 52 57 57
... | 38,336 |
<p>I am calculating a certain statistic(relative entropy) of a certain sequence alignment over DNA sequences. The statistic has a certain distribution in the entire genome of which I only have 1000 sequences of length 1000. I want to test the significance of a certain value of the statistic but I obviously do not know ... | 37,869 |
<p>I have two matrices A and B of the same dimensions. Each cell a(i,j) represents some parameter I'm interested in, and b(i,j) represents the corresponding value in the other matrix. The cells are not interrelated. What's the best way to represent how close these two matrices are? </p>
<p>The entries in these mat... | 44,122 |
<p>Is there any clustering algorithms that:</p>
<ul>
<li>does not assume the number of clusters to be known, and</li>
<li>processes the data in only one pass by considering it as a continuously arriving data stream (and we do not know the data set size beforehand)?</li>
</ul> | 71,627 |
<p>What are some alternatives to Spherical K-Means for clustering very large datasets of high dimension?</p>
<p>I'm looking for something that will be fast even on large datasets, and preferably will not require you to specify the number of clusters to find.</p>
<p>Another property that would be nice (I'm not quite s... | 71,628 |
<p>Anyone that follows baseball has likely heard about the out-of-nowhere MVP-type performance of Toronto's Jose Bautista. In the four years previous, he hit roughly 15 home runs per season. Last year he hit 54, a number surpassed by only 12 players in baseball history. </p>
<p>In 2010 he was paid 2.4 million and he's... | 71,629 |
<p>If I use select if and then list some variables, the output appears as a plain text table in the output viewer.</p>
<p>When I paste this into Excel it all goes into one cell.</p>
<p>I've tried the copy special options and none of them seem to make a difference. Also the columns of data are all separated by differe... | 71,630 |
<p>I know about <a href="http://en.wikipedia.org/wiki/Probability_integral_transform" rel="nofollow">PIT</a>, but this works only when you know the distribution, or at least have a strong hint. What I am trying to achieve is to transform a given sample into an equivalent sample with continuous standard uniform distribu... | 71,631 |
<p>So i have sound files for 5 languages by 2 person, thus my input data has 10 sound files. </p>
<p>Now i want to cluster them based on the languages (thus 5 clusters) and not based on the speaker/voice ( which in case would create only two clusters). but my problem is how do i separate the "language information" fro... | 71,632 |
<p>suppose $X_1,\ldots,X_n$ be random sample of continuous distribution with distribution function $F$ if $$Y=\prod_{i=1}^k F(X_i) \prod_{i=k+1}^n [1-F(X_i)]$$ how can I calculate distribution of $U=-\ln Y$</p> | 33,200 |
<p>I have a matrix A of 1000 observations (rows) and 100 features (cols). I would like to find:</p>
<ol>
<li>Linearly dependent features so that I can remove them and simplify the problem. rank(A) gives me 88, which I assume means that 12 of the features are linearly dependent. Am I right?</li>
<li>After the above ste... | 71,633 |
<p>How can I solve the MLE for the skew-t distribution via EM? I am comfortable with the EM methods for t, so could someone show it for the skew-t?</p> | 71,634 |
<p>I am given a set of regions' macro-economical development indices, such as number of unemployed, gross value added, and so on. Each index naturally is correlated with a size of the region. </p>
<p>I want to visualize differences between the regions preferably with multidimensional scaling. </p>
<p>Before I start, ... | 28,722 |
<p>I'm working on a thesis and I'm using a bit statistics to process the data. I have a certain population and in one sample (N=250) I measure the time it takes to reach a goal. Then I change something in the population that delays that time. I take another sample (N=250) and compare those two. I use a T test to get th... | 71,635 |
<p>I wrote a poker simulator for seven card texas hold 'em, and I found a counter-intuitive result:</p>
<p>If player A starts with a pair of aces against player B who has a random hand, I get a different %win if they share five cards on the board (as it works in Texas hold'em) than if they each have separately drawn h... | 71,636 |
<p>I have two sets of data comparing two variables: x and y. I'd like to transform and compare both sets either in <code>r</code> or <code>matlab</code>.</p>
<p><strong>Scatter plot</strong></p>
<p><img src="http://i.stack.imgur.com/8sB1P.png" alt="enter image description here"></p>
<p>Neither are normal and come fr... | 33,206 |
<p>I want to fit a hyperbolid distribution to my data, in my notation, I have the density
\begin{align*}
H(l;\alpha,\beta,\mu,\delta)&=\frac{\sqrt{\alpha^2-\beta^2}}{2\alpha \delta K_1 (\delta\sqrt{\alpha^2-\beta^2})} exp\left(-\alpha\sqrt{\delta^2+(l-\mu)^2}+\beta(l-\mu)\right)
\end{align*}</p>
<p>with R using Hy... | 33,207 |
<p>I have some data that results from the convolution of a Poisson random process with a decaying exponential, plus some additive Gaussian noise. I'm working on designing a classifier that returns a score which should be proportional to the number of Poisson hits for each time bin from the noisy data.</p>
<p>The data ... | 6,352 |
<p>In the first chapter of the book <em><a href="http://rads.stackoverflow.com/amzn/click/0521864674" rel="nofollow">Algebraic Geometry and Statistical Learning Theory</a></em> which talks about the convergence of estimations in different functional space, it mentions that the Bayesian estimation corresponds to the Sch... | 44,135 |
<p>I have a large data set consisting of the values of several hundred financial variables that could be used in a multiple regression to predict the behavior of an index fund over time. I would like to reduce the number of variables to ten or so while still retaining as much predictive power as possible. <em>Added: ... | 71,637 |
<p>I am learning logistic regression modeling using the book "Applied Logistic Regression" by Hosmer.</p>
<p>In chpaters, he suggested using Fractional Polynomials for fitting continuous variable which does not seems to be related to logit in linear fashion. I tried the <code>mfp</code> package and can give exactly th... | 44,137 |
<p>I have a model needs to transform to log function to perform a linear model, how can I move from $\log(E(Y))= -1.146 + 0.747x$ to get $\hat y = 0.318(1.0776)^x$?</p> | 40,617 |
<p>A norm-table from a psychological test is giving percent ranks (PR).</p>
<p>How can I transform those into t-values by calculation? (Assuming normal distribution.)</p>
<p>I found a lot of references on how to transform z --> t, but none on PR --> t.</p>
<p>Way back in university, we had tables with the bell-curve... | 71,638 |
<p>I've seen lots of mention of this in the implementation of SVDs in various programming environments. What does it actually mean?</p> | 71,639 |
<p>I am trying to fit a multinomial logit model using glmnet. I have a few questions:</p>
<ol>
<li><p>How is the baseline category specified?</p></li>
<li><p>Looking at the model coefficients using coef.glmnet, I'm thinking that many are given by a dot. I assume this means the coefficient was set to zero by LASSO, s... | 71,640 |
<p>I am trying to implement unsuccessfully a function in matlab, to compute the effective sample size after a MCMC chain, with a posterior with 3 coefficients.</p>
<p><img src="http://i.stack.imgur.com/2LaS6.png" alt="enter image description here"></p>
<p>Source: <a href="http://sims.princeton.edu/yftp/Times08/MCMC0... | 71,641 |
<p>I have samples from a highly skewed dataset about users' participation (e.g.: number of posts), that have different sizes (but not less than 200) and I want to compare their mean. For that, I'm using two-sample unpaired t-tests(and t-tests with the Welch’s factor, when the samples had different variances). As I have... | 71,642 |
<p>I have a training dataset $(X, y) \rightarrow z$. Where $X$ is an $n$th dimensional real vector, $y$ is an integer number in $\{1, 2, 3\}$, and $z$ is a real number. I am looking for machine learning algorithm which solves the next problem: $X$ is given and we need to choose $y$ for maximization $z$. I would prefer ... | 71,643 |
<p>In terms of classification task using decision trees, the formula for these looks almost the same. So, how are they different/same? what is the purpose of each in terms of impurity measure?</p>
<p>$\text{Entropy}~(p_1,p_2) = -\sum p_i \log (p_i); i= 1,2;$</p>
<p>$p_i $ are fractions. Say, if I have 2 Yes and 3 No... | 71,644 |
<p>I'm a new R user, and also new to Random Forest modeling. I cannot seem to figure out how to obtain the out-of-bag (OOB) error estimates for cforest models built with the Party Package in R. In the randomForest package, the OOB error estimates are displayed if you simply "print" the model object, but the party packa... | 33,216 |
<p>I suspect this is a statistical problem, but it may be just an algorithmic one. </p>
<p>So, more formally:</p>
<p>Given:</p>
<ul>
<li><p>a set C of unknown ‘canonical' values</p></li>
<li><p>an error window e</p></li>
<li><p>a set V of known values, s.t. every v in V has the property that<br><code>c - e <= v ... | 71,645 |
<p>I'm a statistically incompetent social scientist who is very much out of my depth...</p>
<p>I'm using R to analyse a data set, which is a 1% sample of a population showing cancer rates across 20 regions. There are parameters for male and female rates.</p>
<p>If I have to calculate 95% credible intervals for the me... | 14,455 |
<p><strong>Update: I got the JAGS model running and this eliminates the distracting part of my question. It's really about the proper preparation of data for dinterval() and inits.</strong></p>
<p>I can't find a concrete example of preparing right-censored survival data for use in JAGS when starting with a vector of t... | 71,646 |
<p>Let us say I extract all tweets containing a certain hashtag (main subject of the tweet) and bin them by the hour i.e. count the number of tweets that occurred during a certain hour. I will then be obtaining a time series for this particular hashtag. I have recently come across the <a href="http://cs.wellesley.edu/~... | 71,647 |
<p>Given two time series within the same time period, I can use the <code>ccf</code> function in <code>R</code> to compute a notion of similarity of these time series. What I am wondering is this - can I compute the cross correlation on the trend line obtained after using time decomposition function such as <code>stl</... | 33,221 |
<p>I want to analyse the visual performance, operationalized via contrast threshold, depending on adaptation luminance and spectrum, gathered for 29 subjects. I'm currently kind of confused of how to do that. Some of my data:</p>
<pre><code> ID C_measured Subject LB Spectrum SpectrumLB
1 1 0.1339795 AHI11 0.1... | 33,222 |
<p>I have seen about 16 parameter estimation methods in different research papers. How can these methods be implemented in R language using Monte Carlo simulation technique.</p> | 71,648 |
<p>My problem is interpreting coefficients of such time series model:</p>
<p>\begin{equation}
\ln Y_t - \ln Y_{t-1} =b_1 \cdot \left(X_{t}-X_{t-1}\right)+b_2 \cdot Z_t.\end{equation}</p>
<p>I don't know how to interpret coefficients $b_1$ and $b_2$.</p>
<p>Hope that someone can help.</p> | 71,649 |
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