question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I have a question about OLS estimation bias due to endogeneity. Say I have the following panel regression model for the price of good 1 for a particular sale $k$ at time $t$:</p>
<p>$$P_{kt}^1=\beta M_{t} + \varepsilon_{kt}$$</p>
<p>The price is a function of the market share of a substitute, good 2, and is a func... | g58825 | [
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<p>I've learned that when choosing a number of clusters, you should look for an elbow point for different values of K. I've plotted the values of withinss for values of k from 1 to 10, but I'm not seeing a clear elbow. What do you do in a case like this?</p>
<p><img src="http://i.stack.imgur.com/Uw4ad.png" alt="Troubl... | g19673 | [
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<p>When I start an exploratory analysis on a large data set (many samples, many variables), I often find myself with hundreds of derived variables, and tonnes of different plots, and no real way to keep track of what's going where. Code ends up like spaghetti, because there's no direction from the start...</p>
<p>Are ... | g58826 | [
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<p>Very simply, I'd like to plot a graph that compares what is predicted by the model to the real observations.</p>
<p>It seems easy for binomials, but for multinomial the graph that SPSS creates is pretty ugly, using X and O signs rather than real graphics.</p>
<p>Any clue?</p>
<p>Here's the kind of plot SPSS makes... | g58827 | [
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<p>I have this confusion related to minimization of gaussian likelihood function. The negative of the log likelihood of gaussian distribution is </p>
<p>$-\log \det(Q) + \text{tr}(SQ) + \lambda||Q||_{1}$ where $Q$ is the precision matrix to be estimated</p>
<p>I am following this <a href="http://arxiv.org/pdf/1111.54... | g43079 | [
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<p>I have a binary classification problem, where my training data is 70% positive labeled and 30% negative labelled. I use a logistic loss and it always classifies examples positive on the test data.</p>
<p>How can I make it classify some examples negative as well? One solution I though of might be to remove some posi... | g43566 | [
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<p>According to my notes, stationarity occurs if:</p>
<blockquote>
<p>All the solutions of the characteristic equation of the $AR(P)$,
$1-\phi_1X-\phi_2X^2-...-\phi_PX^P=0$, are greater than 1 in modulus.</p>
</blockquote>
<p>No explanation is given in my notes or textbook. </p> | g58828 | [
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<p>While modelling count outcome data with excess zeros in Stata, we have the zero-inflated versions of both the Poisson and negative binomial models. However, for multiply-imputed data, we do not have the zero-inflated versions of both models. Is there a way for doing zero-inflated Poisson/negative binomial regression... | g58829 | [
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<p><img src="http://i.stack.imgur.com/bsFiQ.jpg" alt="Refer to this for question 4![1]">
<img src="http://i.stack.imgur.com/32AuD.jpg" alt="Refer to this for question 6"></p>
<p>I am trying to find which factors in Ques 6 are strongly related to company being rated high as compared to others in Ques 4 and similarly ... | g14083 | [
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<p>I have a task that involved Bayesian inference and could use some pointers and hints. I've already got some parts figured out but others remain blurred. Also, my OpenBUGS abilities are frankly limited so advice how to concretely proceed with my problem would not hurt.</p>
<p>So the task at hand is following. I am s... | g58830 | [
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<p>I have iid data-points $x_1, \dots, x_n$, generated by an unknown density $f(x)$.
So far I have approximated $f(x)$ with a normal $N(\hat{\mu}, \hat{\sigma}^2 )$, where $\hat{\mu}$ and $\hat{\sigma}^2$ are sample average and variance, but I would like something more flexible.</p>
<p>I have tried with simple Kernel ... | g58831 | [
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<p>Suppose we've ran a logistic regression on some data where all predictors are nominal. With dummy coding the coefficients are ratios of log odds to the reference levels. A colleague claims that we can "solve for $p$" or "apply the inverse logit to the estimated parameters" interpret the result as relative probabilit... | g58832 | [
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<p>I would like to get the significant value and effect size of the independent variable in overall, rather than the normal output from lme4 in R. It is just like the thing people report when running ANOVA. Do you have any idea how I can get this?</p> | g49355 | [
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<p>I have two classes (say <code>1</code> and <code>0</code>), and want to build a classifier. It is possible to use <code>artificial neural networks (ANN)</code> or any <code>"real"</code> classifying method such as <code>SVM</code> or <code>Random Forest</code>.
In case of <code>ANN</code>, one can easily estimates ... | g58833 | [
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<p>Okay, so I need to graph data where 1/2 of the values are around 5, 1/4 of the values are around 400, and 1/4 are around 8000. When I try to do this in excel, I can't even see the values around five. So I am looking for some way to make a graph that somehow displays values of this large range.</p>
<p>(I need to dis... | g49540 | [
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<p>I've seen a reasonable amount of literature about how to choose kernels and bandwidths when computing a kernel density estimate, but I am currently interested in how to improve the time it takes to <em>evaluate</em> the resulting KDE at an arbitrary number of points.</p>
<p>In my case, I'm using a multidimensional ... | g58834 | [
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<p>While it's easy to compute the p-value of Krsukal-Wallis non-parametric test using the <code>kruskal.test()</code> function, I don't know how to compute the mean ranks and standard errors for each group.</p>
<p>For instance suppose the following example:</p>
<pre><code>x <- data.frame(group=rep(1:2,each=10),hei... | g58835 | [
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<p>Statistics emerged as a discipline whose goal was to allow inferences about inaccessible populations from data obtained from its samples. Does modern access to huge amounts of data depreciate the whole discipline of Statistics?</p> | g508 | [
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<p>I am studying how to use genetic algorithm (GA) in clustering analysis on R programming. What I understand now is that we have to determine fitness function in GA. That is, we have to minimize within distance function (I am not sure whether I understand it correctly).</p>
<p>Could anyone point me out how to do clu... | g474 | [
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<p>I have a large set of tweets to which i plan to use cosine similarity to cluster the tweets.
I found NLTK's GAAC to be good but how do i convert the tweets into vectors?</p>
<p>In <code>nltk.cluster.gaac.demo()</code> the data was passed as a vector
<code>[array([ 0.70710678, 0.70710678]), array([ 0.4472136 , 0... | g14088 | [
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<p>If I use the LARS algorithm to fit the LASSO path, is it sufficient to cross-validate using the values of $\lambda$ at each step in LARS or is it better to use a finer grid of $\lambda$ values? I guess I can ask this in two parts: </p>
<ul>
<li><p>Is the prediction optimal model found at one of the LARS steps?</p>... | g58836 | [
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<p>I'm looking for some ideas / perspectives on what can be done when a predictive model is being trained on sample data that is taken over a period of time and the underlying environment is changing (over the course of the sample and continuing in out of sample data).</p>
<p>To be more concrete, I am building an <a h... | g58837 | [
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<p>As part of the inference course in an applied stats masters degree, we've to prepare a talk about convergence (see, for example, Lehmann 1999 Chapter 2). We'll be explaining to other students some concepts and we'll show examples of different kind of convergences by the use of simulation.</p>
<p>It'd be nice to end... | g58838 | [
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<p>I need some resources to get started on using neural networks for time series forecasting. I am wary of implementing some paper and then finding out that they have greatly over stated the potential of their methods. So if you have experience with the methods you are suggesting it will be even more awesome. </p> | g14090 | [
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<p>We have data on the day in which a butterfly pupates (forms a cocoon) in the summer/fall of 2 different pairs of years (2005-2006 vs 2009-2010). At the time that the pupa forms it can either be in diapause (suspended animation) or not. </p>
<p>Individual butterfly caterpillars were randomly selected from a wild p... | g58839 | [
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<p>I have 1000 data for two continuous variables (pressure and temperature). I'd like to calculate Bayesian probability between two variables. </p>
<p>In other words, I would like to determine probability that temperature will increase/decrease if pressure is changed? </p> | g58840 | [
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<p>While studying machine learning, I've read the following statement:</p>
<blockquote>
<p>The kernel $K(x,y)=(x\cdot y+1)^d$ , for $x, y \in \mathbb{R}^p$, has $M={p+d \choose d}$ eigenfunctions that span the space of polynomials in $\mathbb{R}^p$ of total degree $d$.</p>
</blockquote>
<p>I do not understand how d... | g58841 | [
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<p>I have a great interest in learning new methods(at least to me) of variable selection in regards to binary logistic regression when I am working with over 500 potential predictor variables and have the duty of selecting 8 to 15 variables to build a parsimonious predictive model without using the notorious stepwise t... | g58842 | [
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<p>I have records (rows) in a database and I want to compute similar records. I have a constraint to use cosine similarity. If the variables (attributes, columns) vary in type and come in this form:</p>
<pre><code>[number] [number] [boolean] [20 chars string]
</code></pre>
<p>how can I proceed to the vectorization to... | g58843 | [
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<p>I have a dataset of M elements where every item is represented by a feature vector of length N where N is very large and only a small subset of N is bigger then zero for every item. So I have a sparse MxN matrix and I want to cluster these M items.</p>
<p>What tools and algorithms do you advise to use? Any script ... | g14097 | [
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<p>I was reading an article where it mentioned that kernel SVMs have lot more support vectors than linear ones. Can you give me some good references to know about this? </p> | g58844 | [
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0.05212080851197243,
0.0565... |
<p>When would you tend to use ROC curves over some other tests to determine the predictive ability of some measurement on an outcome?</p>
<p>When dealing with discrete outcomes (alive/dead, present/absent), what makes ROC curves more or less powerful than something like a chi-square?</p> | g14098 | [
0.04318060725927353,
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-0.0444754958152771,
0.0266156904399395,
-0.05694786459207535,
0.029026396572589874,
-0.02151... |
<p>How to find a non-trivial upper bound on $E[\exp(Z^2)]$ when $Z \sim {\rm Bin}(n, n^{-\beta})$ with $\beta \in (0,1)$? A trivial bound is obtained for substituting $Z$ with $n$.</p>
<p>A background on this question. In the paper by Baraud, 2002 -- Non-asymptotic minimax rates of testing in signal detection, if one ... | g58845 | [
-0.024935338646173477,
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-0.05378531292080879,
0.08001622557640076,
-0.030981088057160378,... |
<p>I have three terms in my regression models:</p>
<ul>
<li>gender (categorical data), </li>
<li>centeredmeanB (quantitative data) </li>
<li>and the interaction term gender * centeredmeanB.</li>
</ul>
<p>I noticed than the way I coded gender gave me different beta values </p>
<p>If I coded Male: 0, Female:1 </p>
<p... | g21484 | [
0.03387179970741272,
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0.005702956113964319,
-0.08966940641403198,
0.03128797188401222,
0.02867695316672325,
0.04... |
<p>I would like to compare a daily trade w.t.d. $index over the period of 10 years+ versus the shorter term (170 days) using <code>GARCH(1,1)</code>. </p>
<p>The short term data derives from the 10 year+ data. The trouble is that the 10 year time series is heteroskedastic, whereas the shorter data is not. </p>
<p>Can... | g58846 | [
0.03848247975111008,
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0.0012160488404333591,
0.016500448808073997,
0.012920514680445194,
0.08142179250717163,
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<p>we're looking for any software/framework that is able to analyse the financial flux?</p>
<p><em>Some preliminaries</em>. We've been asked by one of our customer to find or develop the software that would solve some their problems. The firm selling a lot of small staff (food elements for animals) in enormous quantit... | g58847 | [
0.028664132580161095,
0.02497652731835842,
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0.03177190199494362,
0.06509014219045639,
0.0... |
<blockquote>
<p><strong>TL;DR</strong></p>
</blockquote>
<p>In the context of a linear regression model, we run a statistical test for whether an estimated coefficient is "statistically significant". We will say that it is if we reject the null of it being zero, for a given type I error.</p>
<p>One can verify that:... | g30540 | [
-0.007210147567093372,
0.012389153242111206,
0.007419229950755835,
0.01322736032307148,
0.03626584634184837,
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0.05909012630581856,
0.02558273822069168,
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-0.04915255308151245,
0.01761886663734913,
0.01800878345966339,
0.05530116334557533,
-0.0052328... |
<p>Let $X\,$ be a non-negative r.v. with known pdf $f(x|\theta)$ but with a single unknown parameter $\theta$. Suppose that the mean $\mu$ can be used to uniquely determine the value of $\theta$, i.e. if given the value of $\mu$, then the value of $\theta$ can be calculated directly. Thus, an alternative way of writing... | g706 | [
-0.00432495167478919,
-0.08177979290485382,
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0.05669416859745979,
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0.03756629675626755,
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0.046862874180078506,
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0.058350443840026855,
0.06615526229143143,
0.030... |
<p>I am a linguist trying to decide on the appropriate statistical test for some data, and I'm a bit at sea.</p>
<p>The data relates to how often participants in bilingual conversations use words from the other language (codeswitches, in the jargon). I want to compare the variance (number of codeswitches) between par... | g38009 | [
0.02951471135020256,
0.0009352713241241872,
-0.0008048114832490683,
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0.025093624368309975,
0.026128999888896942,
0.011404403485357761,
-0.02183639258146286,
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0.010538538917899132,
-0.033332500606775284,
... |
<p>i'm using <a href="http://www.cs.ubc.ca/~murphyk/Software/HMM/hmm_usage.html" rel="nofollow">Kevin Murphy's HMM Toolbox</a>.
But i have a problem in understanding the results.</p>
<p>My problem is to classify some sequences with Hidden Markov Model.
I'm using a (test) dataset build with random sequences of symbol '... | g37813 | [
-0.019844315946102142,
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0.02834712713956833,
0.020548231899738312,
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0.05919268727302551,
0.051399849355220795,
-0... |
<p>Thank you in advance.</p>
<p>I am trying to build a model to predict the possibility of ordinal accident levels in a nuclear station if an accident happens. The accidents include four levels: Site_Area_Emergency, Alert, Unusual Event and Non_Emergency (In order of from Strongest to Weakest, Non Emergency is the wea... | g43132 | [
-0.015233157202601433,
-0.017496922984719276,
-0.007192245684564114,
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0.04079417884349823,
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0.03170393034815788,
0.05534425005316734,
-0.0255420058965683,
-0.03618931770324707,
-0.007846147753298283,
-0.008847963064908981,
0.045414600521326065,
0.... |
<p>I am looking for opinions/interpretation on a model I'm trying to fit. A disclaimer: I'm an ecologist and not a statistician; and I appreciate everyone's time and opinions! I am generally following Zuur et al. 2009's (using R) recommendations in an attempt to model travel speed as a function of a few environmental... | g58848 | [
0.030385877937078476,
-0.06517467647790909,
-0.032741744071245193,
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0.04736018553376198,
0.06899552047252655,
-0.0011058141244575381,
-0.03221603110432625,
0.016845783218741417,
0.058214716613292694,
0.01570127345621586,
0.027812136337161064,
0.0... |
<p>I'm trying to mine that Stack Exchange data dump to find out whether there is a cluster of users that may be positively or negatively affected by the number of badges they've been awarded. The theory I'm working on is that for some people who were motivated by badges, that they eventually lose their appeal and they ... | g43137 | [
0.0007990549202077091,
0.007372645661234856,
-0.025639671832323074,
-0.03751946985721588,
0.043953604996204376,
-0.021312156692147255,
0.07374420762062073,
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0.049466729164123535,
-0.043095335364341736,
-0.008327650837600231,
0.04630555585026741,
0.0652722492814064,
-0... |
<p>I have carried out a study in which I have gathered 3 sentences per participant. These sentences were then classified in 2 ways. I want to test if there are significant interactions between the classifications and find out the effect size. I have done a chi square test for independence and calculated Cramer's $V$ (o... | g58849 | [
0.03340011090040207,
0.021945159882307053,
-0.0019495375454425812,
-0.029839033260941505,
0.008659552782773972,
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0.03285932168364525,
0.020459117367863655,
-0.015665318816900253,
0.03516942635178566,
0.04478001967072487,
0.020941434428095818,
-0.02295590564608574,
0.05... |
<p>I am a web developer and novice statistician.</p>
<p>My data looks something like this</p>
<pre><code>Subject Week x1 x2 x3 x4 x5 y1
A 1 .5 .6 .7 .8 .7 10
B 1 .3 .6 .2 .1 .3 8
C 1 .3 .1 .2 .3 .2 6
A 2 .1 .9 1.5 .8 .7 5
B 2 .3 ... | g58850 | [
0.0017390280263498425,
-0.009841322898864746,
-0.01200195588171482,
-0.06938421726226807,
-0.03720962256193161,
-0.02172129973769188,
0.06358374655246735,
-0.007906443439424038,
-0.01886480301618576,
-0.055327627807855606,
0.021689536049962044,
0.030181849375367165,
0.024309450760483742,
0... |
<p>I have a data set with 925 members that using Easyfit, I've determined is best fit using a Frechet distribution. Now, I'm trying to replicate this functionality in R to determine the optimum fit parameters using the VGAM package. Using this code:</p>
<pre><code>vglm(V1 ~1, frechet2(location = 0), data, trace = FALS... | g58851 | [
0.044259145855903625,
-0.06656770408153534,
0.00001327225527347764,
0.009071040898561478,
-0.002770529594272375,
0.017748134210705757,
0.021868744865059853,
0.009920941665768623,
-0.09826207906007767,
0.01697593554854393,
-0.033824410289525986,
0.04309777915477753,
0.020677467808127403,
0.... |
<p>I was recently looking at some standard error calculations using the following:</p>
<ul>
<li>the formula for the covariance matrix in ordinary least squares (OLS)</li>
<li>the "robust" formula for the heteroskedasticity-consistent covariance matrix</li>
<li>the "modified-robust" formula (also called 'White' for its... | g15 | [
0.001095555373467505,
-0.06061209365725517,
-0.011020558886229992,
-0.005980194546282291,
0.023731300607323647,
-0.024684138596057892,
-0.008992625400424004,
0.0140577033162117,
-0.0018527678912505507,
0.011258319020271301,
0.000553418998606503,
0.022957468405365944,
0.03603828698396683,
0... |
<p>I know there are publicly available datasets for social network graphs (I'm aware of an existing question for that). </p>
<p>But does anyone know if there are any datasets available for user "likes" or interests (Facebook or any other social network)? </p> | g58852 | [
0.0009337873780168593,
0.03281015902757645,
0.005769430659711361,
-0.007433563936501741,
-0.01956724189221859,
0.02900673821568489,
-0.034733377397060394,
-0.026135828346014023,
0.02123497612774372,
-0.037399668246507645,
0.02093614637851715,
0.03937240689992905,
-0.003693037899211049,
0.0... |
<p>In the year 2000, Judea Pearl published <em>Causality</em>. What controversies surround this work? What are its major criticisms?</p> | g58853 | [
0.10559631884098053,
-0.04280310124158859,
0.014122042804956436,
0.004844948183745146,
-0.02782224677503109,
0.0069992863573133945,
0.08474471420049667,
0.030971799045801163,
0.002582297194749117,
0.00017307898087892681,
0.06300392746925354,
-0.0005440934910438955,
0.08267371356487274,
0.0... |
<p>I am trying to solve a linear regression problem with multiple variables in a Hadoop cluster. I was thinking of using SGD to estimate the parameters, but there is one issue I don't know how to solve. The SGD is calculated in parallel through all the nodes of the cluster, and my question is how to combine the output ... | g58854 | [
0.041574377566576004,
0.02177324704825878,
0.004189311061054468,
-0.05711238458752632,
-0.00005879973105038516,
-0.05246126279234886,
-0.043785225600004196,
0.01489629503339529,
-0.04439370706677437,
0.01817256584763527,
0.002851769793778658,
0.030183330178260803,
0.000030485904062516056,
... |
<p>I am modelling the activity of animals (subjects). Each subject is measured for activity repeatedly (which requires a random intercept associated with subject). Subjects have also been measured in two environments (a and b). I specifically want to see if the activity level of a given subject in environment a correla... | g58855 | [
-0.013767029158771038,
-0.032487720251083374,
0.0016043413197621703,
-0.049779292196035385,
0.0072578126564621925,
0.000130205720779486,
0.07799255847930908,
0.008203906007111073,
-0.03884043172001839,
-0.04410732537508011,
0.008416695520281792,
-0.006966882850974798,
0.018834838643670082,
... |
<p>So, I want to estimate the probability that a student will succeed or fail in a particular major (suppose success means in this case to graduate with that major) based on data from that student's application. I have a lot of records of past students' application data and success. </p>
<p>I am aware that I could try... | g47317 | [
-0.044444724917411804,
-0.020979143679142,
0.0062629468739032745,
0.012763348408043385,
-0.08103344589471817,
-0.029125023633241653,
0.03295468911528587,
0.03215760737657547,
-0.052864763885736465,
0.0011708899401128292,
0.005725633818656206,
0.03045778162777424,
0.11184272170066833,
0.021... |
<p>I am attempting to use Akaike's Information Criterion to select the most appropriate model for some data. This means I need to find the likelihood of my data under various models, compute the AIC score for each model, and then select the model with the lowest AIC score. To find AIC, I would use:</p>
<p>$$
AIC = 2k−... | g14113 | [
-0.010933722369372845,
-0.016108842566609383,
0.006331407465040684,
-0.007701046299189329,
0.00028847786597907543,
-0.0321853905916214,
0.0260394848883152,
-0.028692645952105522,
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0.054169103503227234,
-0.021206408739089966,
-0.00008680022438056767,
0.04912925511598587,... |
<p>So, getting an "idea" of the optimal number of clusters in k-means is well documented. I found an <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.109.8192&rep=rep1&type=pdf" rel="nofollow">article</a> on doing this in gaussian mixtures, but not sure I am convinced by it, don't understand it... | g43152 | [
-0.03868211433291435,
0.03566145524382591,
-0.002056811936199665,
-0.052569031715393066,
-0.015756331384181976,
-0.04324231669306755,
-0.07873817533254623,
0.019256126135587692,
-0.026573197916150093,
-0.006629534997045994,
0.03970535472035408,
0.00561633612960577,
0.11753406375646591,
0.0... |
<p>I have two different time serie both length = 100 and I need to know what is the best test (non-parametric, if possible), that return how much these two series are same or similar shapes.</p>
<p>Here are two examples: first one the two series are very similar shape, not matching perfectly but overall trends and top... | g40508 | [
0.01231209747493267,
-0.009663398377597332,
0.005493650678545237,
-0.04728841781616211,
0.0018108341610059142,
-0.02352026104927063,
0.05816768482327461,
-0.07925747334957123,
-0.000654935254715383,
-0.002489150036126375,
-0.02511993981897831,
0.03999396786093712,
0.03489254415035248,
-0.0... |
<p>In Hastie et al's Elements of Statistical Learning, it says </p>
<blockquote>
<p>Least angle regression (LAR) ... can be viewed as a kind of “democratic” version of forward stepwise regression (Section 3.3.2). As we will see, LAR is intimately connected
with the lasso, and in fact provides an extremely efficient ... | g14115 | [
0.06714979559183121,
-0.014941263012588024,
-0.005577831529080868,
-0.00766034284606576,
0.030996738001704216,
-0.028409156948328018,
0.026924319565296173,
0.02123563177883625,
0.003038061549887061,
-0.0015105089405551553,
0.010158303193747997,
0.031923092901706696,
0.07599301636219025,
0.... |
<p>I have generated a vector which has a Poisson distribution, as follows:</p>
<pre><code>x = rpois(1000,10)
</code></pre>
<p>If I make a histogram using <code>hist(x)</code>, the distribution looks like a the familiar bell-shaped normal distribution. However, a the Kolmogorov-Smirnoff test using <code>ks.test(x, 'pn... | g49644 | [
0.02262599766254425,
0.015140151605010033,
-0.01703062281012535,
-0.050283223390579224,
-0.009861002676188946,
0.0005844814004376531,
-0.013186939060688019,
0.06287701427936554,
0.00009935533307725564,
-0.04371792450547218,
-0.03422746807336807,
0.04041329398751259,
0.011492487974464893,
-... |
<p>I have a question relating to the checking for outliers and / or influential points in my dataset using a <code>glmer</code> model with 3 random variables. I'm investigating the detection rate (<code>SumDetections</code>) of receivers over increasing distance (<code>sc.c.distance</code>), and the effect of environme... | g14117 | [
-0.005880311597138643,
-0.0408780612051487,
-0.011310447007417679,
-0.03749886527657509,
0.015514196828007698,
-0.012001450173556805,
0.04998514801263809,
0.028092781081795692,
-0.07345938682556152,
-0.02499128319323063,
-0.025359075516462326,
0.05634889751672745,
0.012224877253174782,
0.0... |
<p>There are several methods to estimate parameters in a model (MLE, MAP, GMM). Does the process of estimating a parameter from historical data have a name?</p> | g14118 | [
0.017523225396871567,
-0.07044277340173721,
0.027803093194961548,
-0.007945266552269459,
0.022442176938056946,
0.010572570376098156,
0.004259111825376749,
0.034275121986866,
-0.04948440566658974,
0.06150761619210243,
-0.03669847548007965,
-0.01439780555665493,
0.06512709707021713,
0.048673... |
<p>In logistic regression, the gradient descent algorithm for calculating coefficients can be
described this way:</p>
<p>Until convergence, do
$$
\beta := \beta + \alpha
\frac{\partial L}{\partial \beta}
$$</p>
<p>where L is the log likelihood function.</p>
<p>Coefficients can be got quite easily here, but how ... | g58856 | [
0.025856632739305496,
-0.056361500173807144,
-0.0062332297675311565,
0.005743143614381552,
0.07827694714069366,
-0.026930829510092735,
0.032264117151498795,
0.03181392699480057,
-0.09706095606088638,
-0.020933520048856735,
-0.08800752460956573,
0.04218847677111626,
0.009068051353096962,
0.... |
<p>I have a dataset where each instance is yes/no for a set of features, and has a score. Let's pretend they're sundaes.</p>
<p>Thus [1,0,1]->6.5
Might mean yes chocolate, no vanilla, yes strawberry with a rating of 6.5</p>
<p>(I actually have 50 features and ~10,000 instances)</p>
<p>I'm interested in seeing which ... | g58857 | [
0.030553176999092102,
0.0003250855952501297,
-0.010613881051540375,
-0.01882191374897957,
0.007389242760837078,
-0.014337421394884586,
0.0023542067501693964,
0.012170667760074139,
-0.0642525851726532,
-0.04648781567811966,
-0.008655998855829239,
0.0169161856174469,
0.08053624629974365,
0.0... |
<p>I am analyzing a public data set of <a href="http://vcdb.org" rel="nofollow">information security incident data</a> and trying to find "clusters" of related factors. </p>
<p>Specifically, each incident is analyzed using <a href="http://veriscommunity.net" rel="nofollow">VERIS</a> for the actor's variety (e.g. actor... | g58858 | [
0.041697483509778976,
0.0671309232711792,
-0.012222903780639172,
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0.0497303232550621,
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0.05313393101096153,
-0.009517478756606579,
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0.03519456088542938,
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0.01092... |
<p>I am fitting several multi-level hierarchical regression models using <code>rstan</code>. Each of these models has a unit information prior over the top-level distribution. The unit priors' parameters were originally store in an R <code>list</code>. My questions are:</p>
<ol>
<li>Do I pass the unit information prio... | g58859 | [
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<p>So I noticed the following phenomena:</p>
<p>I first generate a three-dimensional (x,y,z) multivariate normal distribution with no covariance between the variables.</p>
<p>I then generate a second distribution by rotating the first distribution 90 degrees around the x-axis.</p>
<p>I then perform PCA on each distr... | g14120 | [
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<p>I have a list of p-values from a series of regression equations. Many of these P-values are small. To compute false discovery rate I have been using the q-value package in R. I notice, based on this analysis, that P-values of 0.05 correspond to q-values that are smaller than the p values (0.03). Would I then say th... | g58860 | [
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<p>Hope i'm posting in the right thread.</p>
<p>I have a sample of genes where I calculate a number of features in the start of each gene, and a number of features in the end of each gene. I plotted the results in 2 curves, one is the number of features in the start of each gene, and the other one is the number of fea... | g14122 | [
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<p>I am trying to use <code>lqmm</code> to fit some models and it appears to be working ok with my data (N 2000 w/ clusters=1200). I am using a call like this:</p>
<pre><code>lqmm (y~x + covariates , random=~1,group=subjectID, iota=c(0.25, 0.50, 0.75),...)
</code></pre>
<p>However, I am getting these optimization err... | g14123 | [
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0.0693... |
<p>Suppose we have identified $20$ cases from a population of $1000$ people. $15$ of these cases are male. We want to use one-to-one matching to choose the control group. We would match on gender. So would we just randomly choose $15$ males from the population that are not cases and then arbitrarily match them to the $... | g14124 | [
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<p>This is a general question, has probably been asked before (I searched and did not see similar), may have a simple answer, may be ridiculous, and is just to satisfy my own curiosity.</p>
<p>Say we build a linear model (or any model for that matter) on our training data, and then generate predictions from our test d... | g43159 | [
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<p>In library "lmtest" The jtest and coxtest functions are used to see if two non-nested models are equivalent.</p>
<p>According to the help function:</p>
<pre><code>jtest performs the Davidson-MacKinnon J test for comparing non-nested models.
coxtest performs the Cox test for comparing two non-nested models.
</co... | g14126 | [
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<p>I have several variables that describe the quality of a trading relationship between a client and financial institutions (FIs) the client deals with. The variables are populated with observed data over a period of time. Lets call the variables A,B,C,D. The client is able to use this data to filter on FIs based on e... | g58861 | [
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<p>I'm comparing various conditions versus some disease for a large stratified/clustered dataset which purports to account for the entire population after weighting -- hence the use of RR instead of OR. An epidemiologist colleague suggested that I include relative risk in my analysis, but I feel that the version of the... | g14127 | [
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<p>I've been doing glm and thought I had it cracked but looking at some sites for interpreting results I realised R had displayed my results oddly. </p>
<pre><code>> glm(Number.of.Fish~Julian.Date*Size.Class,na.action=na.omit,poisson)
Call: glm(formula = Number.of.Fish ~ Julian.Date * Size.Class, family = poisson,... | g58862 | [
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0.04308238625526428,
0.02973904274404049,
-0.020... |
<p>I am using a one-way independent MANCOVA with 4 dependent variables and a single covariate. My predictor is bivariate. I'm currently trying to test for heterogeneity of regression in SPSS by assessing the interaction between the covariate and predictor. The question is whether I should test the interaction for each... | g14128 | [
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0.03849583864212036,
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-0.011437260545790195... |
<p>from <a href="http://www.stat.berkeley.edu/~breiman/RandomForests/cc_home.htm#unsup" rel="nofollow">http://www.stat.berkeley.edu/~breiman/RandomForests/cc_home.htm#unsup</a> :</p>
<blockquote>
<p>Formulating it as a two class problem has a number of payoffs. Missing
values can be replaced effectively. Outliers ... | g58863 | [
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0.022639654576778412,
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0.026834573596715927,
0.06863722950220108,
0... |
<p>I'm trying to do an exact paired permutation test. What does this "mapping" mean?</p>
<pre><code>> library(exactRankTests)
> perm.test(rnorm(10), rnorm(10), paired=TRUE, exact=TRUE)
1-sample Permutation Test (scores mapped into 1:m using rounded scores)
data: rnorm(10) and rnorm(10)
T = 6, p-value = 0.... | g58864 | [
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<p>I have a data frame in R containing four variables. I ran a PCA which showed that first two principal components mostly explain much of the variance in my data. I know that principal components are linear combinations of the original variables. Now how do I find out which combination(s) of my original variables give... | g14130 | [
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<p>How is it that lowering the number of frequence,$n$ by $1$ in the for formula for Population and Sample Variance account for the discrepency of using sample rather than population.</p>
<p>I mean how is dividing the whole expression by $n-1$ in sample variance better than dividing by $n$?</p>
<p>I am referring to t... | g58865 | [
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<p>I have a dataset of ~400 subjects. For each subject, I have about 18 variables (V1...V18), all of those continuous and measured at the same timepoint.</p>
<p>A paper I'm working on would benefit from showing that one of those variables (say V1) has a significant correlation with one of three other variables (say V2... | g58866 | [
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<p>I just started learning regression, so my background is not very strong. I have to solve a certain problem, which doesn't seem too hard, however I have some trouble in understanding it.</p>
<p>Suppose we define </p>
<pre><code>x<-seq(1,50,1), y<-3*x+2+6*rnorm(length(x))
</code></pre>
<p>Hence my response $Y... | g58867 | [
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<p>I am trying to decide on an approach to estimate design effect for a multi stage cluster survey. The clusters were selected with probability proportional to size sampling WITH replacement. The primary sampling units (districts) are large enough that some were sampled multiple times. When defining the PSU variable... | g14133 | [
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<p>I have a question? which clustering algorithms is good to detect any kind of significant changes, named as “Event” in real time event ,specially for spatial temporal analysis
of Flicker, Twitter databases </p> | g49929 | [
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<p>I ran an ANCOVA which proved that the covariate is significant. If i understood right, the estimated marginal means show what are the means of the DV when we account for the covariate. Then we could compare them to the means from the descriptive statistics and see what is the difference under the influence of this c... | g58868 | [
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<p>Maximum Likelihood is given by the formula</p>
<p>$h_{ML}=arg\space max_{h \in H } \space\space p(D/h)$</p>
<p>I want to transform it in terms of mechanism involved in Expectation maximization.</p>
<p>$h_{ML}=arg\space max_{h \in H } \space\space p(D/h)$</p>
<p>$\implies h_{ML}=arg\space max_{h \in H } \space\sp... | g58869 | [
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<p>In my experiment, I am varying 4 different parameters (<code>side</code>, <code>eccentricity</code>, <code>latency</code> and <code>duration</code>), and for each of these conditions I have 2 or 4 values (e.g., <code>eccentricity</code> can be <code>5 deg</code> or <code>10 deg</code>, <code>side</code> can be <code... | g14137 | [
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... |
<p>I have the following likelihood function:</p>
<p><img src="http://i.stack.imgur.com/1d5Tw.gif" alt="enter image description here"></p>
<p>I'm given this information about the $\Omega$ matrix ($\boldsymbol{1}$ is a $T \times 1$ vector of ones):
<img src="http://i.stack.imgur.com/YLjFa.gif" alt="enter image descript... | g58870 | [
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0.03055... |
<p>I have two questions: </p>
<ol>
<li><p><em>Which regression should I choose and why?</em> </p>
<p>Based on the R squared value, exponential regression seems to be a better fit. But I am not really sure, if I should just go with it because it has a higher R squared value?</p>
<p><img src="http://i.stack.imgur.c... | g14139 | [
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<p>Suppose we’re building a system with certain qualities that we’re interested in, e.g. response time, battery usage, etc. Each of the system’s qualities depends on our decision about components we use to build the system. We only know how the <strong>decisions</strong> impact the <strong>qualities</strong> of our sys... | g58871 | [
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<p>On seeing the following table, I concluded there is a lot of sparseness in the 'very unsafe' category. My first reaction was to merge it with the 'unsafe' category, leaving me with 3 categories. But another option is to just delete the category. What are the considerations to make before choosing one option? Also, I... | g58872 | [
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<p>I am a biology student. We do many Enzyme Linked Immunosorbent Assay (ELISA) experiments and Bradford detection. A 4-parametric logistic regression (<a href="http://www.miraibio.com/blog/2010/08/the-4-parameter-logistic-4pl-nonlinear-regression-model/" rel="nofollow">reference</a>) is often used for regression these... | g58873 | [
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<p>I have been working on some data in collaboration with a statistician. As the data was not normally distributed a log-transformation was performed. However, it was explained to me that we cannot report effect sizes of our findings in the original units because of this transformation. We therefore resorted to using p... | g58874 | [
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<p>I frequently measure multiple variables, in multiple replicates, at many sites. For instance, I might measure bacterial abundance and bacterial growth rates, each in 3 replicates, at many sites. Each replicate is independently sampled <em>and</em> each variable is measured in a different sample (i.e., I can't measur... | g58875 | [
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... |
<p>Are there any non-identical distributions which happen to have the same moment-generating function?</p> | g43192 | [
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-0.04537821188569069,
0.03633147478103638,
-0.015454425476491451,
-0.02924787811934948,
-0.02589457668364048,
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-0.00589934503659606,
-0.053675733506679535,
-0.04345232993364334,
0.002364677144214511,
-0... |
<p>Will running multiple regression including 2 independent variables give the same output for each independent variable if we run linear regression using the same independent variables separately/individually?</p> | g43193 | [
0.00638936460018158,
-0.03977428376674652,
0.0259998869150877,
0.041910890489816666,
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0.0019017922459170222,
0.05986256152391434,
-0.0662873163819313,
-0.016... |
<p>Could you please tell me which R function/library (not necessarily R) to use to plot Nemenyi's test result with the critical differences?</p>
<p>Below there is an example which was retrieved from <a href="http://support.sas.com/resources/papers/proceedings12/129-2012.pdf" rel="nofollow">this</a>* paper (page 9).
<... | g58876 | [
0.011560937389731407,
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0.015370369888842106,
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0.0063260989263653755,
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-0.0015868721529841423,
0.04579351097345352,
0.01078858133405447,
0.03114345110952854,
-... |
<p>I ran "mvn" using the "mclust" package in R using the following codes:</p>
<pre><code>mvn("EEE", data[,18:22], prior = NULL, warn= NULL)
</code></pre>
<p>I am having trouble figuring out how to tell if the results are indicating "multivariate normal fit". The results are below:</p>
<pre><code>$n
[1] 707
$d
[1] 5... | g21500 | [
0.005938010755926371,
-0.05635908618569374,
-0.017254887148737907,
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0.024477802217006683,
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-0.008693207055330276,
-0.02866368182003498,
0.04564250260591507,
0.008526329882442951,
0.034... |
<h3>Background</h3>
<p>I have a data set of patients who were operated on at two different hospitals, A and B. Lymph nodes were removed from each patient during the operation and counted, this is saved as <code>LN_reviewed</code> for each patient. I want to know how much variability there is in the lymph node number t... | g14150 | [
0.020422223955392838,
-0.03819315508008003,
0.0040561361238360405,
-0.04520614072680473,
-0.02198232151567936,
0.0034628647845238447,
0.04538574069738388,
0.009602110832929611,
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0.0006850818172097206,
0.0022348484490066767,
0.06462785601615906,
0.04366564005613327,
-0... |
<p>I run the following linear model in R :</p>
<pre><code>lm(formula = NA. ~ PC + I(1/SPCI), data = DSET)
</code></pre>
<p>The p-value for each predictor is significant, and it works fairly well with respect to most of the assumptions in linear regression, such as:</p>
<ul>
<li>Normal distribution of errors.</li>
<l... | g14151 | [
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0.0037953995633870363,
0.03564804419875145,
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0... |
<p>If you would fit a small sample like with the standard framework for linear models. Would you suggest from the residuals any special correlation structure like compound symmetry or first order autoregression?</p>
<pre><code>Y<-data.frame(response=c(10,19,27,28,9,13,25,29,4,10,20,18,5,6,12,17),
tre... | g58877 | [
0.03283599764108658,
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0.0028613214381039143,
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-0.04888823255896568,
0.025474710389971733,
-0.00031588232377544045,
0.0034943160135298967,
... |
<p>Which test should I use to test the difference of monthly opinion poll?</p>
<p>If I want to know whether the poll result of April is significantly different from March, should I use independent t test or paired test?</p>
<p>If I use independent t test, it seems that I am comparing two groups of people instead of c... | g58878 | [
0.03409568965435028,
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0.015467185527086258,
0.0054614669643342495,
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0.03087626025080681,
0.03280588984489441,
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0.025845088064670563,
0.09401404857635498,
0.013240472413599491,
-0.022793196141719818,
0.003422... |
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