question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>I have a bilot of PCA and am not able to correctly interpret it.</p>
<p>There are two type of whiskies and both have two unmatured treatments and two matured treatments, and compounds relating to each treatment are shown with their concentration. If you can see the snapshot of the data and plot below, I can see tha... | 32,706 |
<p>I am a database developer working for a sales and manufacturing business. I am mostly ignorant about statistics. We need useful metrics. Our managers are tuned to accounting, and the vagaries of production tend to confound us. We do very little measuring of our production, and what we have is poorly formed. I s... | 71,323 |
<p>Assume a stochastic process with observation $r$, and two hypotheses : $X \sim (0, \sigma^2)$ and $Y \sim (0, \sigma^2 + \tau^2)$. When we observe/receive $r$ we don't know which hypothesis $X$ or $Y$ it came from. Is there any way to have an estimate $\hat{\sigma}^2$ for the variance $\sigma^2$ under these condit... | 32,708 |
<p>I would just like to know what are the differences between kernel classifier and linear classifier?</p>
<p>In what kind of problems the first is used and in what kind the second?</p>
<p>What could be the advantages of the one over the other?</p> | 32,710 |
<p>So I have a dataset of dimension 6395x15 and when I apply kernel-PCA on this dataset, I get a rotated matrix of dimesion 6395x596. pcv() gives me the matrix of column-wise eigen-vectors and this matrix is also of dimension 6395x596. My question is how can I project a new data or my test data onto these eigen-vectors... | 71,324 |
<p>I'm trying to understand how multiple regression statistically controls for the effects of other predictor variables when calculating partial regression slopes. In a multiple regression of Y~X1+X2, would the partial regression slope of X1 be given by [Y]~[residuals of X1~X2], or by [residuals of Y~X2] ~ [residuals o... | 71,325 |
<p>Suppose you know $Y \sim N(\mu_1, \sigma_1^2)$ or $Y \sim N(\mu_2, \sigma_2^2)$. You observe $Y=y$, some realization of the random variable $Y$. What is the probability that $Y \sim N(\mu_1, \sigma_1^2)$?</p>
<p>My intuition is to compare $p$-values from each distribution. Let $p_i$ be the $p$-value for $y$ under $... | 49,870 |
<p>I knew about "Coordinate descent" and "Gradient descent" algorithms before; they are well-known and Wikipedia has articles for those. However I recently came across an algorithm called "Coordinate gradient descent". </p>
<p>How does this algorithm exactly work, and how does it relate to "Coordinate descent" and "Gr... | 32,713 |
<p>I am trying to apply the idea of mutual information to feature selection, as described in <a href="http://cs229.stanford.edu/notes/cs229-notes5.pdf">these lecture notes</a> (on page 5).</p>
<p>My platform is Matlab. One problem I find when computing mutual information from empirical data is that the number is alway... | 43,538 |
<p>I have time series data and I used an $ARIMA(p,d,q)+X_t$ as the model to fit the data. The $X_t$ is an indicator random variable that is either 0 (when I don’t see a rare event) or 1 (when I see the rare event). Based on previous observations that I have for $X_t$ , I can develop a model for $X_t$ using Variable Len... | 71,326 |
<p>I'm trying to compute the Gini index on the SO reputation distribution using SO Data Explorer. The equation I'm trying to implement is this:
$$
G(S)=\frac{1}{n-1}\left(n+1-2\left(\frac{\sum^n_{i=1}(n+1-i)y_i}{\sum^n_{i=1}y_i}\right)\right)
$$
Where: $n$ = number of users on the site; $i$ = user serial id (1 - 1,225... | 43,540 |
<p>All my independent variables are stationary at their levels except one variable which became stationary after first difference i.e. my dependent variable. Can I still conduct co-integration test ?</p> | 9,469 |
<p>Does Adaboost ensure that resultant accuracy is more than or at least equal to current accuracies?</p>
<p>What happens if <strong>Classifier A</strong> performs badly and the weights are accordingly updated and the next <strong>Classifier B</strong> performs very well (better than <strong>Classifier A</strong>) on ... | 32,715 |
<p>Does anyone know of an explicit matrix expression for the covariance of a linear and quadratic form? That is,</p>
<p>$\mathrm{Cov}[\mathbf{a' y},\mathbf{y' Hy}]$
where $\mathbf{y}\sim \mathcal N(\boldsymbol{\mu},\boldsymbol{\Sigma})$.</p>
<p>I'm particularly interested in the case where
$\boldsymbol{\mu}=\mathbf{... | 47,992 |
<p>Say clustering was performed. My concern is to understand what characterizes certain cluster. Which variables differ most for a certain cluster? Are there any methods for performing such kind of analysis?</p>
<p>For example, say I have 50 variables and 10 clusters. The desired result would sound like: for a cluster... | 32,717 |
<p>Can SVM-LIGHT generate MAE (mean absolute error) and RMSE (root mean square error) for svm's model performance?If we using libsvm,can libsvm generate MAE and RMSE too by using windows command?</p> | 71,327 |
<p>What are alternative measures of the prediction power of a model, apart from the coefficient of determination $R^2$? What are their strengths and weaknesses, especially in comparison to the $R^2$?</p> | 303 |
<p>Imagine I wish to see the effect of some treatment on the correlation between two groups of variables, which I measure with Spearman's rank correlation coefficient.</p>
<p>Treatment A gives a Spearman's rank of 0.4, 0.44, 0.43 for my 3 replicates.</p>
<p>Treatment B gives a Spearman's rank of 0.48, 0.45, 0.46 for ... | 48,019 |
<p>Following my previous <a href="http://stats.stackexchange.com/questions/27936/statistical-test-for-finding-significant-positions-having-deviated-values">question</a>, I used Dixon test for outliers with the help of Michael Chernick answer. So now I have pvalues for say 10 numbers (basically 10 patients). But I have ... | 71,328 |
<p>If you fit a linear model or a mixed model there are different types of codings available to transform a categorical or nominal varibale into a number of variables for which paramaters are estimated, such as dummy conding (the R default) and effects coding.</p>
<p>I heard that effects coding (sometimes called devia... | 32,718 |
<p>I have a question regarding data screening for an exploratory factor analysis (EFA). </p>
<p>I am conducting an EFA to identify the factor structure of 20 questions that I created on the topic of spirituality. I want to identify outliers in my sample using mahalanobis distances, and I am doing this on SPSS using a ... | 71,329 |
<p>This is question 5 is from Staudte and Sheather (1990), Robust estimation and testing.</p>
<p>Let $X_1,\ldots , X_n$ be i.i.d with $$ F_\theta = F(\frac{x}{\theta}),\quad x>0;\theta>0.$$ Assume that $T_n = T_n(X_1,\ldots ,X_n)$ is scale equivariant. Show that $$\mathbb{E}[T_n] = \theta \mathbb{E}_1[T_n]$$. </... | 32,723 |
<p>How strong/weak of a correlation is this?</p>
<pre><code> Exposure
No Yes Total
FALSE 139 467 606
Disease TRUE 11 104 115
Total 150 571 721
OR = 2.81
Exact 95% CI = 1.45, 5.97
Chi-squared = 10.49, 1 d.f., P value = 0.001
Fisher's exact t... | 37,847 |
<p>I'm designing a clinical trial that will evaluate a behavioral therapy against a control condition, and I'm looking for some good texts on this topic. There are a lot of books on clinical trials in medicine, but I've had a hard time finding one that also covers the topics specific to psychotherapy research. </p>
<p... | 48,054 |
<p>A survey is being administered in a resource intensive setting. A 2-phase study design will be implemented using cases and controls identified by a certain behavior (say, smoking) and they will be screened for SNP information on a number of biomarkers for disease associated with the negative health outcomes associat... | 71,330 |
<p>I use several control variables and<br>
use independent variable $A$ for model 1,<br>
use independent variable $B=1-A$ for model 2,<br>
use independent variable $C=A-E-F$ for model 3,<br>
use independent variable $D=A-C-F$ for model 4,<br>
use independent variable $F=A-C-D$ for model 5. </p>
<p>I have to report co... | 71,331 |
<p>I've just started working with Bayesian models.
My question is in the context of hierarchical Bayesian model.</p>
<p>Suppose you have <em>n</em> models to train. However, some of these models are similar to each other in some sense and I could assume that they their parameters are drawn from the same prior distribu... | 48,058 |
<p>I am looking a bit on the effect of bootstrap on bias. I came by the following example in the estimation of variance (when dividing by n instead of n-1). Can someone explain to me why the bias when using the mean of a bootstrap sample comes out smaller than when using the simple mean?</p>
<p>R code:</p>
<pre><code... | 32,724 |
<p>I'm new to data science and have a problem finding clusters in a data set with 200,000 rows and 50 columns in R. </p>
<p>Since the data have both numeric and nominal variables, methods like K-means which uses Euclidean distance measure doesn't seems like an appropriate choice. So I turn to PAM, agnes and hclust whi... | 71,332 |
<p>Can anyone show me how to calculate the expected number of 95% confidence interval of a binomial distribution using R, such as $\text{Bin}(100,0.5)$.</p> | 32,726 |
<p>I am not sure if this is the correct place to ask this kind of question, I hope it is. I am studying this <a href="http://arxiv.org/pdf/1012.4571" rel="nofollow">paper</a> on an improvement of Elo rating system called Elo++. On page 4 the author states that he want minimize a function called <em>total loss</em> that... | 43,551 |
<p>Consider the lognormal random variables $X_1$ and $X_2$ with $\log(X_1)\sim \mathcal{N}(0,1)$, and $\log(X_2)\sim \mathcal{N}(0,\sigma^2)$.</p>
<p>I'm trying to calculate $\rho_{\max}$ and $\rho_{\min}$ for $\rho (X_1,X_2)$. One step in the given solution I have is:</p>
<p>$\rho_{\max}=\rho (\exp(Z),\exp(\sigma Z)... | 30,249 |
<p>I'm heavily into role-playing systems, scripted a set of utilities in ruby for pen-and-paper games and I sort of understood statistics when I took it, but I could never for the life of me figure out the following:</p>
<p>Given a varying-length series of independent 50/50 probabilities, i.e. 2, 3, 5 or 7 coin tosses... | 71,333 |
<p>I have data regarding the number of deaths in a city over 35 years. I've collated the data, and now wish to prove the difference in total number of deaths between seasons is significant. Spring has 631 deaths, summer 540 deaths, autumn 502 deaths and winter has 605 deaths. Clearly there is a big difference between s... | 32,732 |
<p>I have data that looks like this:</p>
<pre><code>011100111110100111
111111111111110010
111100001111000011
</code></pre>
<p>1D lanes of streams of data. Each row signifies the presence of a thing at that time with a 1 or a 0. Things tend to exist in consecutive chunks across the stream. The vertical order of the ro... | 43,557 |
<p>Sorry I am a stats newbie, I understood that I can use the search feature, I tried to search but I am afraid that I am not using the right terms and the results returned are not quite relevant to my question. </p>
<p>I have a set of data readings (50 cases), A is a number between [0,1] and B is {yes,no}. My hypothe... | 71,334 |
<p>Let $Y_{t} \sim N(0,\sigma_{Y_t}^2) $ (independent var), $X_{t}\sim N(0,\sigma_{X_t}^2)$ (dependent var) be time series variables. However, suppose we don't observe $Y_t$ and instead measure it with some error. That is, we have access to $\hat{Y}_t = Y_t - \nu_t$. Assume that the measurement error is of the form $\n... | 32,734 |
<p><strong>Here is the situation:</strong>
I have an individual level data set $X$ where each row is a person $i$ and each column denote characteristics of $i$. The problem is that my data is missing an important variable, lets call this $z_{i}$. </p>
<p>To resolve this situation I am considering using <strong>data im... | 71,335 |
<p>In SVMs, is the solution to the minimization problem $$\textbf{w} = \sum_{i=1}^{n} \alpha_i x_i y_i $$ and once we know $\textbf{w}$ we can get $\textbf{b}$?</p>
<p>In plain English can somebody please describe the solution above? Basically the hyperplane that separates the data with the maximum margin is a linear ... | 71,336 |
<p>currently finishing the last year of PhD in statistics, we wonder if you could help us with the following.</p>
<p>Let $T = [0,1]$ and $X = \left( X_{t}, t \in T \right)$ be a gaussian process with mean function $m$ and covariance function $W$. Parentheses in functions are omitted in this notation. We write $X \sim ... | 71,337 |
<p>From Wikipedia</p>
<blockquote>
<p>The Net Promoter Score is obtained by asking customers a single
question on a 0 to 10 rating scale, where 10 is "extremely likely" and
0 is "not at all likely": "How likely is it that you would recommend
our company to a friend or colleague?" Based on their responses,
cu... | 71,338 |
<p>I'm running a model with an interaction term, of the general form:
$Y=b_1X_1+b_2X_2+b_3X_1X_2$, whereby $X_2$ is a dummy variable and $X_1$ is continuous.</p>
<p>Neither $X_1$ nor $X_2$ turn out as significant. However, a $t$-test of the hypothesis that $X_1$ is significant when $X_2=1$ (i.e. $H_0: X_1+X_2=0)$ turn... | 32,740 |
<p>I'm in the process of folding FastDTW into my SVM and the question now is how to best format my data (irrespective of normalization). Here's an example of what I'm attempting to do - given two 3d vectors:</p>
<p>A:</p>
<pre><code>10.3, 5.4, 2.3
7.2, 4.9, 1.4
5.9, 6.2, 3.1
9.2, 4.2, 2.5
2.5, 7.2, 4.2
</code></pre>
... | 71,339 |
<p><a href="http://jmlr.org/proceedings/papers/v28/lopes13.pdf" rel="nofollow">Estimating Unknown Sparsity in Compressed Sensing</a> is a paper about sparse signal. I am just learning the concepts. In the first paragraph, it says that when the number of observation data samples $n$ is less than the signal dimension $p$... | 12,283 |
<p>After reading Chapter 3 in the Elements of Statistical Learning (Hastie, Tibshrani & Friedman), I wondered if it was possible to implement the famous shrinkage methods quoted on the title of this question given a covariance structure, i.e., minimize the (perhaps more general) quantity
$$(\vec{y}-X\vec{\beta})^TV... | 71,340 |
<p>What does it mean when people say that a T-test performed on ranked data is equivalent to a Mann WHitney U -test? Does that mean they just test the same hypothesis/are useful in the same situations or are they are supposed to give the exact same p-values? The reason I ask is I tried both in R and compared two groups... | 71,341 |
<p>my problem is the following: having a distribution function of daily casfhlows resulting from electricity trading, I need to calculate a yearly 99% VaR, i.e. the 1% percentile of yearly casfhlows distribution. </p>
<p><strong>Method 1/</strong> Use CLT - fast and easy, albeit daily cashflows show some autocorrelati... | 43,569 |
<p>Does anybody encountered or derived a spatiotemporal version of Hammersley and Clifford theorem? The original theorem (with the proof by Besag) fits just for the temporal models, but if I have a sample of data, that was collected at different times in the same locations, than I need also to incorporate a temporal ef... | 43,570 |
<p>I performed and plotted a kmeans analysis in R with the following commands:</p>
<pre><code> km = kmeans(t(mat2), centers = 4)
plotcluster(t(mat2), km$cluster) #from library(fpc)
</code></pre>
<p>Here is the result from the plot:<img src="http://i.stack.imgur.com/sBWIS.png" alt="enter image description here">... | 37,485 |
<p>I have some pairs of datasets (<code>n=200</code> or thereabouts), of samples which are non-negative and not normally distributed. I think these pairs of variables are related, probably linearly. </p>
<p>Calculating Spearman's rank correlation on these datasets gives some strange results. The correlation coefficien... | 32,746 |
<p>As a part of a design of experiments course I'm taking, I ran an experiment at home. The experiment was checking how water boiling time changes under certain factors (5 overall factors) all which had 2 levels: with or without salt, with or without oil, type of pot, type of water and the diameter of the pot. The expe... | 71,342 |
<p>I am having difficulty turning unstandardized RMR estimates from AMOS software output in a SEM into standardized estimates to enable suitable interpretation. Can someone give me advice on where to start with this?</p> | 18,406 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/298/in-linear-regression-when-is-it-appropriate-to-use-the-log-of-an-independent-va">In linear regression, when is it appropriate to use the log of an independent variable instead of the actual values?</a> </... | 49,325 |
<p>I am looking at attachment and cyber addiction. I'm carrying out an four-way Anova, attachment patterns being my ivs (secure, preoccupied, fearful and dismissing) with cyber addiction as my dependent variable. I am intending to use 100 participants in my study, I wanted to know if that is an appropraite amount to ru... | 71,343 |
<p>I would like to use a clustering method, e.g. 'mclust', in R to classify each individual in my dataset to k groups. I have 7 continuous and 3 categorical variables. These and other hierarchical clustering methods do not allow for use of categorical variables. Searching Google and this site it appears that converting... | 43,576 |
<p>I have some multivariate data and want to investigate the effect of some environmental gradient. I want to use capscale but I don´t know how to deal with the permutation scheme. I have made up some artificial data, with 20 sites along a gradient ("env"):</p>
<pre><code>######### create some species data along a gra... | 37,845 |
<p>I would like to ask a question about Gower similarity/dissimilarity index.
Is it ok to use the Gower dissimilarity measure with Ward linkage clustering?
I was reading that the Gower similarity index should not be used with Ward linkage because the index is not metric.
I was wondering if this is only the case for th... | 71,344 |
<p>My dataset consists of 4-million records, each a combination of age, race, and a discrete observed value. The goal is to find a correlation between the combination of age/race and the observation, so that given a distribution of ages and races, a distribution of expected observations can be calculated.</p>
<p>I am ... | 43,581 |
<p>This is a general question about performing data analysis.
I have a data set with ~1000 sample size and 200 features. Some of features have more than 50% missing or even higher. The missing pattern is unclear to me. I plan to do regression.
Any one can provide some reference where should I start and what is the corr... | 71,345 |
<p>So I've been learning about AB Testing and have used it to examine the form conversion rate of two different forms. However, I'm curious about testing whether a form with ads will generate more revenue than a site with just a form and no ads.</p>
<p>So the two things I'm comparing:</p>
<pre><code>- form with ads
-... | 48,277 |
<p>I'm performing logistic regression for binary classification in SAS and it outputs all of the coefficients to the logit model. </p>
<p>I was wondering how you would take those coefficients and use them to convert the model into a linear hyperplane in the original space (i.e., hyperplane that splits the space into t... | 32,752 |
<p>In my work in online marketing, we frequently run A/B or multivariate web page tests. The Key Performance Indicator for these tests is overall Revenue. The treatment that nets the most revenue, either by influencing more conversions to sale, or by influencing a user to spend more per transaction, or a combination of... | 71,346 |
<p>Let $r(\pi, \delta)$ denote the Bayes risk of an estimator $\delta$ with respect to a prior $\pi$, let $\Pi$ denote the set of all priors on the parameter space $\Theta$, and let $\Delta$ denote the set of all (possibly randomized) decision rules. </p>
<p>The statistical interpretation of John von Neumann's minimax... | 71,347 |
<p>i have built a neural net class object using <a href="http://www.inside-r.org/r-doc/nnet/nnet" rel="nofollow">http://www.inside-r.org/r-doc/nnet/nnet</a> and i am trying to access values returned by that object.</p>
<p>Values section of page <a href="http://www.inside-r.org/r-doc/nnet/nnet" rel="nofollow">http://ww... | 71,348 |
<p>I'm not sure how this would look. It seems you've have to specify regime breakpoints within the data, right? Or is there some rolling method that could compare window sizes against each other?</p>
<p>Also key, is it possible to do this without specifying a model?</p> | 71,349 |
<p>Imagine the following data:</p>
<pre><code>ds <- data.frame(x=1:10,y=1:10,z=rep(c("A","B"),each=5))
</code></pre>
<p>the means for groups in <code>z</code> are:</p>
<pre><code>library(plyr)
ddply(ds, "z", function(x) mean(x$y))
# z V1
#1 A 3
#2 B 8
</code></pre>
<p>do a couple of models:</p>
<pre><code>m1... | 71,350 |
<p>I often find myself training several different predictive models using <code>caret</code> in R. I'll train them all on the same cross validation folds, using <code>caret::: createFolds</code>, then choose the best model based on cross-validated error.</p>
<p>However, the median prediction from several models often... | 32,754 |
<p>I have a question that might be trivial but I have not much knowledge on that method:
I want to estimate a structural model with GMM and my model works in the sense that it estimated the right coefficients of simulated data. This works fine without adding a gradient (I'm using "gmm"-package in R), just the vcov-matr... | 32,755 |
<p>Accidents occur with a Poisson distribution at an average of 4 per week. i.e., $\lambda= 4$.</p>
<ol>
<li><p>Calculate the probability of more than 5 accidents in any one week.</p></li>
<li><p>What is the probability that at least two weeks will elapse between accident?</p></li>
</ol>
<p>Query: Is is necessary to ... | 81 |
<p>I am trying to understand code vector in self organizing map. </p>
<p>Could anybody explain me intuitively what it is exactly?</p> | 71,351 |
<p>Suppose I have a list of measurements from an experiment; for example,</p>
<blockquote>
<p>34 31 55 18 19 22 44 48 23 . . .</p>
</blockquote>
<p>But I then learn that these experiments were conducted by two different technicians, so I embolden those conducted by tech #1, and I leave untouched the measurements of... | 43,594 |
<p>I'm teaching linear algebra to a class of engineers, social scientists and computer programmers. We just did singular value decomposition, and we have an extra day, so I thought I'd talk about the relation between singular value decomposition and principal component analysis. I have the theory part of the lecture wr... | 32,756 |
<p>I'm trying to analyze a part of European Social Survey data.<br>
The outcome has to be treated as continuous, however it can take only discrete values from 1 to 6. The predictor variable is age. I fitted a simple linear regression model and now I need to check model's assumptions.I have this residuals vs. predictor ... | 71,352 |
<p>I have some images that are made of an object and some amount of background noise. I have sampled the object for example at 40%. So the object is becoming pixelated, then I inject some amount of noise to the object. I know that formula for SNR is:</p>
<pre><code>SNR = 20log10 (Signal/Noise)
</code></pre>
<p>Accord... | 71,353 |
<p>I am using the following regression:</p>
<p>$$\text{Test score} = \beta_0+\beta_1\text{Mother's employment}+\beta_2\text{Mother's education}$$</p>
<p>where "Mother's employment" is a set of dummy variables indicating whether the mother works more than 35 hours a week, is unemployed or <strong>is absent</strong>, a... | 71,354 |
<p>I measured a binary variable from two different populations, and now I'm trying to find out whether the different populations differ with regards to this variable. I could use a Chi-Square test, but that would necessitate that both populations have the same length. Is there an appropriate test for these circumstance... | 71,355 |
<p>Does there exist any agreement on what must rejection regions look like topologically? If we identify the region of "acceptance" with the corresponding confidence interval (or confidence region in dimensions greater than 1) then, according to <a href="http://stats.stackexchange.com/questions/15872/are-confidence-int... | 71,356 |
<p>I have a dichotomous variable which I am trying to predict. In order to do this I have about 2000 variables out of which 1100 are continuous variables (real values between 0.0 and 1.0) and the rest are categorical variable (0 or 1).</p>
<p>I am a total newbie and would like to know how to go about it. I am not awa... | 32,761 |
<p>I have a dataset of around 100 different subjects</p>
<p>Some of them have a disease, some do not (roughly 60:40 disease:no disease)</p>
<p>They are subjected to a battery of 15 tests, to see if they are outside "normal" ranges.</p>
<p>Just plotting the values for the different tests for disease vs. non-disease a... | 71,357 |
<p>Given two independent variables with Beta distribution, $X \sim \text{Be}(a_1, b_1)$ and $Y \sim \text{Be}(a_2, b_2)$, how do you find the probability that the value of X is greater than the value of Y for a given observation?</p>
<p>Does this probability have a name that I'm just blanking on?</p> | 32,763 |
<p>I would like to test for stationarity in cointegration. I intend to use an augmented dickey fuller test.</p>
<p>However, I need one for c# - either a library or the source code.</p>
<p>Or is your have source in a similar language c, java I can implement.</p>
<p>Thanks</p> | 71,358 |
<p>I am conducting a <a href="http://en.wikipedia.org/wiki/Lexical_decision_task" rel="nofollow">Lexical Decision Task</a> where my dependent random variable is Response Time (RT). </p>
<p>My experimental design consists of 5 blocks of a 100 trials each. In each block, 50% of trials correspond to one experimental cond... | 71,359 |
<p>When creating some observed data, I want to use a stochastic parameter but I do not want the stochastic parameter to be affected by this data - I don't want its likelihood to be affected by this data set. Is there a way to do that (I apologise if I have made any errors of terminology!)</p>
<p>To be more concrete I ... | 71,360 |
<p>I have two data.tables which correspond to each other:</p>
<pre><code>ACTid<-read.table("ACTid.txt") %# Categorical input factor (1x1000)
Y<-read.table("Y.txt") %# Continuous output (1x1000)
>ACTid
...
992 1
993 1
994 1
995 6
996 3
997 6
998 3
999 1
1000 1
>Y
...
992 1.074105e+01... | 32,766 |
<p><strong>Context</strong>: Both dependent $(Y_1,~Y_2,~Y_3)$ and independent $(X_1,~X_2,~X_3)$ variables were measured repeatedly at three time points, $\text{Time}_1$, $\text{Time}_2$, and $\text{Time}_3$. Moderator $M$ is a continuous variable measured on one occasion, and is hypothesized to be unchanged throughout... | 71,361 |
<p>What makes you to believe that statistics is something is worth to think about. Isn't that a fake science?
Do you think that statistics is a real science?
Do you think statisticians should be paid?</p> | 71,362 |
<p>I am classifying data points from two different groups using <code>LibSVM</code>.</p>
<p>I do the following:</p>
<ol>
<li>Creating the input file for <code>LibSVM</code>. In the input file, I put all the data I have.</li>
<li>Scaling it (using <code>svm-scale</code>).</li>
<li>Using <code>grid.py</code> of <code>l... | 71,363 |
<p>I have a classifier that I want to use on short documents and I need to improve quality of the corpus used for training. I have 250,000 documents and manual inspection is expensive.</p>
<p>The collection of short documents has been pre-labelled by a collection of rules as good or bad. The accuracy of this pre-pro... | 71,364 |
<p>Assume we have a set of histograms, let's say they describe age distribution of some people.</p>
<p>We want to translate this:</p>
<pre><code> x
x x
x x x x x x
</code></pre>
<p>to: <em>mostly young</em>; and this:</p>
<pre><code> x
x x x
x x x x x x
</code></pre>
<p>to: <em>mostly middle-age</em>; ... | 32,769 |
<p>I am running a generalised linear model in R. I have a single response variable and a maximum of 4 possible explanatory variables. I am adding each explanatory variable to the model sequentially, based on whether the coefficient is statistically significant. </p>
<p>If the coefficient for an explanatory variable is... | 32,771 |
<p>I'm using the lasso function in MATLAB to perform regularized regression for parameter selection. I'm new to LASSO, so I generated some toy data and tested LASSO with lambda = 0 to make sure I would get the OLS result (since there would be no penalty for model size). Unfortunately, I'm getting a value pretty close t... | 37,734 |
<p>I am preparing a graph for publication: it has 3 panels, and two groups (line graphs) in each panel, with error bars at each time point.</p>
<p>For one of the panels, the last time point (with fewer observations) has quite wide error bars. </p>
<p><strong>Is there a hard and fast rule about the range of the y-axis... | 71,365 |
<p>Given 2 sets of test scores (the same students take both tests), I'd like to transform them such that they can be added to give a combined score.</p>
<p>The 2 tests have different variances, so adding them directly wouldn't work. Dividing each score by the standard deviation of that test then adding is better but t... | 71,366 |
<p>Over the past few days I have been trying to understand how Markov Chain Monte Carlo (MCMC) works. In particular I have been trying to understand and implement the Metropolis-Hastings algorithm. So far I think I have an overall understanding of the algorithm but there are a couple of things that are not clear to me ... | 43,616 |
<p>I build confidence bounds for estimating PDF of the empirical sample using bootstrapping:</p>
<pre><code>data <- rnorm(1000)
d <- density(data)
boot <- replicate(100,
{ x <- sample(data, replace=TRUE);
density(x, from=min(d$x), to=max(d$x))$y})
CI <- apply... | 32,773 |
<p>I want suggestions about learning and predicting some object's position before hitting one out of four sides of a wall. I have some priority according to side of wall, and of course all the scenarios would be in 3D space having <code>x,y,z</code> coordinates of the object's trajectory coordinates. The simple scenari... | 71,367 |
<p>I'm performing classification with the libSVM package in R and am wondering about the correct procedure for weighting or up-sampling. I have a data set that is 19,396 observations of which only 81 are the positive class. Since I'm dealing with such an unbalanced data set I would like to use weighting or up-sampling ... | 48,478 |
<p>Consider a simple regression (normality not assumed): $Y_i = a + b X_i + e_i$ where $e_i$ is with mean 0 and standard deviation $\sigma$. Are the Least Square Estimates of $a$ and $b$ uncorrelated? </p> | 49,871 |
<p>I have a big dataset of +- 40000 observations, each containing 784 variables. Because this dataset is extremely large I want to perform a dimension reduction. </p>
<p>Now everywhere I read that I can use PCA for this. However, I still don't seem to get what to do after calculating/performing the PCA. In R this easi... | 49,524 |
<p>Please explain the meaning of 'order of integration' when talking about cointegration.<br>
An explanation with some examples would be great.</p> | 30,583 |
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