question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>As far as I can tell this question has never been asked before. There are several questions that touch on related issues, but as far as I can see none of them have provided a definitive answer to this question. Furthermore, in at least one case the most upvoted and second most upvoted answer have implicitly disagree... | g63429 | [
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<p>I am interested to know if we have 3 dependent variables, and 2 independent variables, online and face to face, with 2 levels each, as in the example below. The sample size is 30 for each mode of study - 30 participants for online mode and 30 for face to face.</p>
<ol>
<li>What type of ANOVA do we need to conduct?<... | g21094 | [
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<p>I am a student and am new to statistical market research.</p>
<p>Is it possible to analyze the dependence of answers to one Likert-type item on answers to another Likert item (predictor)? If so, what test can I use?</p>
<p>I am doing an analysis of how much attachment/affinity (dependent Likert item) of consumers ... | g63430 | [
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<p>In meteorology we have the concept of monthly rainfall, which is just the sum of daily rainfall over that month. Now, given this extreme example:</p>
<h3>Situation 1:</h3>
<pre><code>First day of month: 210mm
All remaining days: 0mm
Monthly rainfall = 210 + 0 + ... + 0 = 210mm
</code></pre>
<h3>Situation 2:</h3>... | g63431 | [
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<p>I have a dataset of approximately 100 objects. For each object, I have made measurements and have a handful of values (typically less than 10). </p>
<p>I also know several physical properties of my objects. My dataset is arranged thusly: <em>(arbitrary numbers)</em></p>
<pre><code> Measurement1 Measureme... | g63432 | [
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<p>Is there any particular reason you will choose the kernel density estimation over the parametric estimation? I was learning to fit distribution to my data. This question came to me. </p>
<p>My data size is relavtively large with 7500 data points. Auto claims. My goal is to fit it to a distribution(nonparametric or ... | g42742 | [
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<p>I think that a formulation of SVM for points x with label y is :</p>
<p>$$
\begin{align}
\arg\min_{\substack{u,w,b}} \frac{1}{2} \cdot |w|^2 + C \cdot \sum_{i} u_i \\
s.t.\ \ y_i\cdot (w \cdot x_i + b) &\geq 1-u_i \\\\
u_i \geq 0 \\
\end{align}
$$</p>
<p>In that formulation, if we take C = 0, what pre... | g38436 | [
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<p>I’m working on a classification system which consists of an auto-encoder for feature learning and logistic regression for classification. The system has five hyper-parameters as enumerated below.</p>
<ol>
<li>Number of features it's learning via auto-encoder</li>
<li>Weight decaying parameter of the auto-encoder</l... | g63433 | [
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<p>I have a PDF (Probability Density Function) generated from a vector of 1,000,000 empirical values. This empirical PDF is heavily skewed to the right.</p>
<p>In this form, I can't make accurate predictions using a linear regression.</p>
<p>To fix this, is there some method to find the function F(x) to transform (i.... | g361 | [
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<p>I am learning the SVM classification and especially interested in applying to medical data. Now, I encounter a problem and do not know if this dilemma has a terminology for it. </p>
<p>Assume that there are samples of healthy people ( of both gender) and people with liver cancer ( of both gender). If we label h... | g40212 | [
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<p>Suppose I want to turn statistical significance of 0.05 into a z-score of ~1.64</p>
<p>Can I use a normal distribution to convert these?</p> | g63434 | [
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<p>I am having difficulty understanding nested effects. Suppose 20 people each are assigned to treatment groups A B C and D. Would it be correct to say that Person is nested within treatment group? So for example, for each subject within each treatment group, each subject underwent 10 trials and for each trial, his hea... | g63435 | [
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<p>I understand deriving a covariance matrix from phylogenetic data to make $cov(X,Y) = 0$ for two variables you're making a regression on. But what happens if you have one continuous variable, that you've previously shown to be dependent on phylogeny, and one ordinal variable? The latter being ordinal, I'm not sure ho... | g63436 | [
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<p>Let's say I have to make a multiple regression like:</p>
<p>$ Y_i = \beta_0 + \beta_1 x_i + \beta_2 w_i + ... +\beta_3 z_i + \epsilon_i $</p>
<p>Then I run a Ramsey RESET test upon it and discover that my linear specification is not good. What is the best way to cope with non-linearity? I know that I could specify... | g63437 | [
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<p>Given <strong>n</strong> random variables <strong>x1,...,xn</strong> (one-dimensional).
The following is known (corr() = Pearson correlation):</p>
<pre><code>corr(x1,x2) = a
corr(x2,x3) = a
</code></pre>
<p>The actual values of the random variables are unkown though. Only some of their correlations are known.</p>... | g21104 | [
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<p>I am trying to implement the sparse PCA algorithm in scikit-learn, and it is giving me the following user warning:</p>
<pre><code> UserWarning: Regressors in active set degenerate.
Dropping a regressor, after 1 iterations, i.e. alpha=1.836e-05,
with an active set of 1 regressors, and the smallest cholesky pivot e... | g21105 | [
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<p>I am running simulations and I need to run a Cox model with a certain baseline hazard. The data are generated with a constant baseline hazard $A$ and I need to run coxph using this data but instead of estimating baseline hazard using Breslow formula, I need R to use baseline hazard=$B$). Is there a way to do it?</p> | g21106 | [
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<p>I've seen a <a href="https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CDEQFjAA&url=http://repositorium.uni-osnabrueck.de/bitstream/urn%3anbn%3ade%3agbv:700-2008112111/2/E-Diss839_thesis.pdf&ei=RCm6UYW9CIeCjAKunIGYDw&usg=AFQjCNHTNmf0AAetC8N4hgJFErKcK... | g63438 | [
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<p>I have a data set that is imbalanced and would like to weight the samples to compensate, however I can't find code to implement this in R though I believe there is a feature in the <code>randomForest</code> package to do this.</p>
<p>Here's a sample dataset :</p>
<pre><code>id buy=1/noBuy=0 timeOnSite(sec.... | g40404 | [
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<p>I hope to apply a Survival Model framework to a problem, but I'm not sure that I have sufficient data.</p>
<p>My data are from a repeated series of surveys, where sampled respondents are asked if an event has occurred. My problem is, while I know the precise time at which each respondent's spell <em>starts</em>, th... | g63439 | [
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<p>From <a href="http://onlinelibrary.wiley.com/doi/10.1002/0471667196.ess1595/abstract" rel="nofollow">Encyclopedia of Statistical Sciences</a> I understand that given $p$ dichotomous (binary: 1=present; 0=absent) attributes (variables), we can form a contingency table for any two objects <em>i</em> and <em>j</em> of ... | g63440 | [
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<p>I am trying to analyze some prevalence data and estimate the effect on prevalence of some health condition of an intervention that was introduced at some time point. The data concern a number of clusters and I have summary data (number of diseased and cluster sizes) for each cluster, at each discrete time point. The... | g63441 | [
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<p>My colleagues and I are looking for guidance on how we might compute a common effect size (ES) from the following measures of association:</p>
<ul>
<li>Pearson's r</li>
<li>Spearman's rho</li>
<li>Kappa</li>
<li>ICC / intraclass correlation</li>
<li>Yule's q</li>
</ul>
<p>All garnered from completely different set... | g63442 | [
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<p>I'm using R to compute robust multiple linear regression.
I use the command <code>rlm</code> from the package MASS.</p>
<p>As psi function I use <code>psi.huber</code> or <code>psi.bisquare</code>.</p>
<p>Is there a way to get an estimator of the goodness of fit of the model? Maybe something comparable to the Adju... | g63443 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/25605/why-anova-regression-results-change-when-controlling-for-another-variable">Why ANOVA/Regression results change when controlling for another variable</a> </p>
</blockquote>
<p>I have used SPSS to run ... | g49674 | [
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<p>I am trying to do text classification using Naive Bayes. Before training, I would like to make feature selection in order to reduce the feature space dimension. In order to do so, I have thought of using a method that weights 2 filters for scoring the features and then select the top K features.</p>
<p>For example,... | g63444 | [
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0.052... |
<p>If I have two positive real numbers that can take on any value between 0 and some finite real number, how do I normalized the difference between these two numbers to [0,1] interval
where 0 indicates no similarity and 1 indicates that these two numbers are the same?</p>
<p>Thank you in advance. </p> | g49598 | [
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<p>I decided to use RFE using the caret package for feature selection for a logistic regression model.</p>
<p>The documentation says the Varimp for linear model uses </p>
<p>the absolute value of the t-statistic for each model parameter is used.</p>
<p>Logistic regression is not a linear model or has any of the line... | g21113 | [
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<p>I have got two wind datasets (one for 4 months and the other one for 12 years). Typically wind speed distributions follow Weibull distributions. In order to demonstrate my data distribution in a statistically sound manner, I ran goodness of fit test in Minitab. However, all p-values of 16 distributions including Wei... | g63445 | [
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<p>I have a bunch of data that's both positive and negative. Its calculated from the residuals of an ANOVA (i.e. specific leaf area calculated as the residuals of an ANOVA of leaf area with leaf blade weight). Right now the data is not homoscedastic or normal. Since I can't log negative numbers I'm unsure of how to mak... | g4263 | [
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-... |
<p>Imagine an experiment where you roll two fair, six-sided dice. Someone peeks at the dice, and (truthfully) tells you that "at least one of the dice is a 4". What is the probability that the total of the dice is 7?</p>
<p>It seems straightforward to calculate that the probability the total is 7 is 2/11.</p>
<p>Howe... | g21115 | [
0.012161694467067719,
0.033523865044116974,
0.03230978175997734,
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0.06689351052045822,
0.009557398967444897,
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0.02... |
<p>I know that this issue was already discussed here but I faced with the problem I can't solve. I have list of persons, each represented with some time series consisting from 4-8 points. I want to approximate them all with the function $y=a\cdot x^2\cdot exp(-bx)+c$.
Thus for each person I am going to find his own "a"... | g21116 | [
0.003036702750250697,
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0.... |
<p>I am learning Machine Learning (Linear Regression) from <a href="https://www.coursera.org/course/ml" rel="nofollow">Prof. Andrew Ng's lecture</a>. While listening when to use normal equation vs gradient descent, he says when our features number is very high (like $10^6$) then to use gradient descent. </p>
<p>Everyt... | g14236 | [
0.019266445189714432,
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0.06501495093107224,
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-0.0032711289823055267,
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0.030169477686285973,
0.1038556694984436,
0.0... |
<p>I am implementing an EEG classifier with 15 subjects (patients), specifically a support vector machine classifier.</p>
<p>I randomly choose the training and testing sets, but I was faced by a question "how did you choose subjects in each set?". I looked for the response but I couldn't find a good one (cross validat... | g21118 | [
-0.014720025472342968,
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0.002464147750288248,
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0... |
<p>I am doing an analysis where I am using one data set of 12 rows (Mold), and running a linear regression analysis on this data set to generate two different linear regression equations. </p>
<p>From there I use these 2 linear regression equations to predict 2 values (EDGgm, EDGww) on a different data set (Box). Then... | g63446 | [
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0.009713164530694485,
0.054781198501586914,
0.07271242141723633,
0.02044... |
<p>This problem is about maximum likelihood estimation. Let $f\left(x;\theta\right)$
be a parametric density function with unknown parameter $\theta$,
and denote $\theta_{0}$ the true value. By Jensen's inequality, we
have $E_{0}\left\{ \log f\left(x;\theta\right)-\log f\left(x;\theta_{0}\right)\right\} \leq0$,
where $... | g63447 | [
0.01876765675842762,
0.020830340683460236,
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0.01284877024590969,
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0.013173524290323257,
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0.04268467053771019,
0.003... |
<p>I'm interested in references for running empirical Bayes (EB) in conjunction with MCMC. The closest thing I've found to what I'm looking at is a surprisingly recent and somewhat obscure paper <a href="http://www.stat.lsa.umich.edu/~yvesa/EB.pdf" rel="nofollow">available here</a>, and seems to suggest an improved ver... | g63448 | [
0.02752574533224106,
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0.012645450420677662,
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0.014026913791894913,
0.020066646859049797,
0.015993280336260796,
0.08901910483837128,
0.04303... |
<p>If my variables all take on integer values between 0 and 10, where 0 represents dissatisfied and 10 is very satisfied, would this mean my variables are categorical?</p> | g63449 | [
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0.00996480230242014,
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... |
<p>I am trying to investigate the following problem using multinomial likelihoods and could really do with some advice regarding its appropriateness and implementation in R.</p>
<p>A sequence is generated by selecting with replacement from a bag of n differently coloured balls and consists of the number of occurrences... | g21122 | [
-0.0016661541303619742,
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0.036076538264751434,
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0.047398507595062256,
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<p>I am trying to formally compare the distribution of the likelihood values generated using two different models with marginal posterior values of the parameters obtained using MCMC in order to assess whether one model is good enough approximation to the other one. Both models have the same number of parameters, the... | g21125 | [
0.015277700498700142,
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0.025247368961572647,
0.02899499423801899,
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0.... |
<p>When you do a Principal Component Analysis (PCA), your dataset generally looks like the following one:</p>
<pre><code>Country Var1 Var2 Var3
A 2 18 23
B 3 16 28
C 1 19 33
</code></pre>
<p>But what happens, when you have more than one observati... | g21126 | [
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0.055673930794000626,
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... |
<p>I use some insurance quote data with demographic data as variables and the target is binary (0,1). The total observations is around 50,000 and the variables are around 60. The demographic data is based on zip code(not individual), so I divided them by total population in that region. So the demographic data is betwe... | g24901 | [
-0.018908562138676643,
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-0.05062088742852211,
0.024903541430830956,
0.02277846820652485,
0.022926613688468933,
-0... |
<p>How can I say better for a MCMC in terms of speed? I'm confused with several measures of speed of convergence. I know some people compute the second largest eigenvalue of transition probability matrix. Some compare autocorrelation coefficients. And some others calculate relaxation time.</p>
<p>Is there a well accep... | g63450 | [
0.04561107978224754,
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0.006485807243734598,
0.022710800170898438,
0.01962326467037201,
0.06546451151371002,
0.05742... |
<p>I need to do a 12 month rolling crime rate. I have monthly crime counts and population counts every 3 months.</p>
<p>For a calendar year I would usually use a population from mid-year as the denominator and the crime rate for the year as the numerator and then standardise using, say, 100,000. (i.e. crime count / po... | g63451 | [
0.06049157679080963,
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<p>A while back I asked a question about <a href="http://stats.stackexchange.com/questions/17462/correlating-time-stamps">correlating times between time stamps</a> and <a href="http://stats.stackexchange.com/a/22333/7482">received a response</a> from Peter Ellis that said I could calculate mean distances between codes.... | g21128 | [
0.01794538088142872,
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0.013399994932115078,
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0.02979724295437336,
0.0007346919155679643,
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-0.03690938279032707,
0.006686622742563486,
0.017832240089774132,
0.06183034926652908,
0.0... |
<p>I have three estimates for $\alpha$, $\beta$ and $\gamma$ (let's call them $\hat\alpha$, $\hat\beta$ and $\hat\gamma$). I also have the variances of each estimate, and their covariances.</p>
<p>I want to do a multiple hypothesis test where the null is that $\alpha=1$ and $\beta=1$ and $\gamma=1$. What is the formul... | g63452 | [
0.015170454047620296,
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0.012282476760447025,
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-0.03192625567317009,
-0.030137252062559128,
0.021582206711173058,
-0.0164159145206213,
... |
<p>For a project I need to build a model that can predict batch processing time for the steps in a manufacturing process that are performed on a specific tool type. I know that the processing time is a function of the batch size (number of individual pieces of product loaded into the equipment at once) and the step in ... | g21129 | [
0.01239621639251709,
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0.005397485103458166,
0.0013240132248029113,
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0.06289505958557129,
0.008279126137495041,
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-0.02935766987502575,
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0.018330050632357597,
0.022999150678515434,
0.... |
<p>What are the considerations that we need to take into account if we need to transform just the explanatory variables (not the dependent variable). I have data on assets and liabilities and I need to use assets-liabilities or net worth as the explanatory variable. I can't use logarithm because net worth can be negati... | g63453 | [
0.048288844525814056,
0.0035614718217402697,
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0.004527626559138298,
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0.015042503364384174,
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0.02247452922165394,
0.04970325157046318,
0.0158... |
<p>If My data for a logistic regression analysis came from different surveys, is it still random? For example, modeling whether a person chose finance as their major. Can I take data from a survey that just focused on the characteristics of finance majors (1) and combine it to surveys made just focused on the combined ... | g21130 | [
-0.002258937107399106,
0.005364058073610067,
0.029130244627594948,
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0.0022985124960541725,
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0.005705866497009993,
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0.023308854550123215,
-0.04634669050574303,
0.03339845687150955,
0.0064208232797682285,
0.01994442567229271,
-... |
<p>Suppose $X$ is distributed $N(\mu, \sigma^2)$ where $\mu \neq 0$.<br>
Can I use the Delta Method to say that $log(X)$ ~ $N(log(\mu), \sigma^2/\mu^2)$?</p> | g63454 | [
0.013275963254272938,
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0.05527303367853165,
0.03147215396165848,
0... |
<p>If I do a Bayesian mcmc search with a flat prior such as uniform distribution with very large lower and upper limits, then multiplying the likelihood by the prior equates to simply multiplying the likelihood by a constant, and there is no reason to leave the constant/prior in the model. In such a case, it would see... | g63455 | [
0.01377866044640541,
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0.03468998521566391,
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0.024121606722474098,
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0.0018823308637365699,
-0.0032094642519950867,
0.009050336666405201,
0... |
<p>I'm trying to fit a gumbel distribution to the following dataset using the VGAM function.</p>
<pre><code>1
5273101
14729731
1061376
449451
16
554221
96306
21716
1013682
34720
</code></pre>
<p>In doing so I recieve the following error:</p>
<blockquote>
<p>In checkwz(wz, M = M, trace = trace, wzepsilon = control$... | g38611 | [
0.058805912733078,
-0.009643028490245342,
0.021304482594132423,
-0.04054225981235504,
-0.0010238359682261944,
-0.01828806847333908,
0.049548666924238205,
0.013272670097649097,
-0.007645877078175545,
-0.0071777235716581345,
0.006290890742093325,
0.01680966652929783,
0.02232637070119381,
-0.... |
<p>I would like to create a function to determine annual chance of flooding given a specific ground elevation. The data I have available to me are water surface elevations at 5 specific recurrence intervals <code>(10yr, 25yr, 50yr, 100yr, and 500yr)</code>. My initial approach was to run a linear regression using a l... | g21132 | [
0.028568033128976822,
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0.0704445019364357,
0.01608024165034294,
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0.04511202499270439,
0.04802103713154793,
-0.026... |
<p>I've been reading "A primer of multivariate statistics" by Richard J. Harris, page 546, which shows how to derive the Hotelling $T^2$ statistic, after seeing <a href="http://stats.stackexchange.com/questions/43968/hotelling-t2-test-derivation-question">this related but different question</a> (I have the degrees of f... | g202 | [
0.0017685819184407592,
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0.01019459031522274,
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0.027761023491621017,
0.04994277283549309,
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0.009553427807986736,
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0.04141034930944443,
0.0255918987095356,
0.018... |
<p>I am working with a binary predictive model for data that belongs to A and B. The learning sample that I am using contains 6000 row that belongs to group A and 1000 row that belongs to group B. I would like to make my learning sample equal in number for both variables (i.e. 1000 row that belongs to A and 1000 row th... | g26361 | [
0.011682678014039993,
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0.0422457791864872,
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0.012715373188257217,
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0.023079365491867065,
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0.019921278581023216,
0.07469716668128967,
0.017635593190789223,
0.020720399916172028,
0.02... |
<p>I have time series data with multiple instances. For example, instances like (<code>0.36,0.35,0.32,0.31,0.31,0.30,0.30,0.28,0.30</code>) occur 20 times ($20\times 9$ array). I am wondering how to do variance stabilization with boxcox transformation. Is connecting all instances to form one long series so boxcox is ap... | g21134 | [
-0.018020525574684143,
0.023988740518689156,
0.008187240920960903,
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0.022110719233751297,
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0.02880769595503807,
0.02336479350924492,
0.... |
<p>I've been working with some process cycle time data and scaling using the standard z-score in order to compare between parts of the full cycle time. </p>
<p>Should I use some other transformation since the data are heavily right-skewed/non-normal? ('outliers' can never take negative time and often take much longer ... | g63456 | [
-0.00041060574585571885,
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0.040026746690273285,
0.017693517729640007,
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0.0215192511677742,
0.004928694572299719,
0.027215706184506416,
0.028500918298959732,
0... |
<p>This is a natural experiment, so I can not 'resample':</p>
<p>My population has a property with 9 possible values: 1,2,3,9.
Each value has a probability associated with it. For example 1's occur 10% but 2's occur 7% in the population. </p>
<p>For my sample (n = 1000), I measure the percentage of the sample that e... | g21138 | [
-0.011752454563975334,
0.015534143894910812,
0.0005274619907140732,
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0.007931483909487724,
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0.01403760351240635,
0.05088265985250473,
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-0.0020462286192923784,
-0.0008191718370653689,
-0.013939480297267437,
-0.005597060080617666,... |
<p>I am looking to find the power of a study using a G*Power post-hoc test for a repeated measures within-between design. I have the effect size calculated, alpha set at .05, my sample size, and number of groups. I have 8 different measures that are each averaged from two-three reps. All 8 measures are muscle activity ... | g63457 | [
-0.017941435799002647,
-0.006814230233430862,
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0.02444157563149929,
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0.02618984691798687,
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... |
<p>I am creating a support vector machine for extremely unbalanced data in which identifying instances of the rare class is of the highest importance. Since the data is so unbalanced, training and testing a model with no up-sampling results in an extremely accurate model that performs very poorly in terms of its true p... | g40432 | [
-0.03242148458957672,
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0.01871589757502079,
0.05765596777200699,
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0.030647525563836098,
0.0... |
<p>I am assigned with a academic task to forecast temperature using CurveFitting.</p>
<p>Please suggest me whether I use Linear regression/ Non-Linear regression or extrapolation? I have to forecast 1 next week (days from 16 to 23) temperature.</p>
<pre><code> days=[1:15];
temp=[34 36 38 35 36 37 4... | g63458 | [
0.03607461228966713,
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0.005811878480017185,
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-0.014595073647797108,
0.039883702993392944,
0.0008997153490781784,
-0.03164952993392944,
0.002207111334428191,
0.017220478504896164,
-0.0050160945393145084,
0.017621401697397232,
... |
<p>I am developing a regression model and most of my variables are 0/1 variables. </p>
<p>Should these variables be treated as factor variables in the model or can they just be left as numeric 0,1?</p> | g63459 | [
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<p>I want to approximate the distribution of a binomial random variable $X\sim B(n,p)$. In all references I have seen it is done by a normal distribution. (Of course the Central Limit Thm and de Moivre–Laplace thm are good justifications for it.) Doesnt though the truncated normal distribution on [0,n] give a better ap... | g63460 | [
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... |
<p>I have a derived dataset that specifies the percentiles from the 10th to 95th in increments of 5 along with the total number of data points. Is there a way to estimate the mean of the original dataset?</p> | g63461 | [
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<p>If I have a system of equations, $Ax=B$ where the elements of $B$ have been experimentally determined and as such each element has some uncertainty, how would I propagate this to the elements of $x$? </p>
<p>$$
\left[\begin{matrix}
a_{11} & a_{12}\\
a_{21} & a_{22}\\
\end{matrix}\right]
\left[\begin{matrix}... | g63462 | [
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<p>EDIT: Already got an answer to question 4 (programming). Question will remain on theoretical issues about factorial experiment designed in blocks and Duncan's test.</p>
<p>Given one experiment designed in blocks and with a full factorial scheme with two independent variables with two levels each (2 x 2): </p>
<pr... | g63463 | [
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0... |
<p>I'm not sure the best way to explain this, so let me give an example that motivates my question. I have tried reading the RPART manual, documentation, and its code, but I have not been able to resolve this.</p>
<p>Let's build two classification trees from the iris data: one using only 2 predictors (Sepal.Width &... | g2010 | [
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<p>While studying about probability distributions I found that distributions such as $\chi^2$ only would be able to tell if there <strong>is</strong> or there <strong>is not</strong> relation between a variable, but not how strong it is. </p>
<p>Later, it is pointed out that it is possible to observe how strong this r... | g21149 | [
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<p>Consider estimating the variance of a RV $X$, we start with the sample variance:</p>
<p>$$
\begin{array}{ll}
V_1 & = \frac{1}{N-1} \sum_{i=1}^N (X_i - \bar{X})^2\\
& = \frac{1}{N-1} \left(\sum_{i=1}^N X_i^2 - 2\bar{X}\sum_{i=1}^N X_i + N\bar{X}^2 \right)\\
&= \frac{1}{N-1} \left(\sum_{i=1}^N X_i... | g40446 | [
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<p>I'm trying to aggregate $T$ local image descriptors (i.e. histograms) into a vector, namely, the Fisher Vector as described in this paper by H. Jégou et al., <a href="http://hal.inria.fr/inria-00633013/" rel="nofollow">Aggregating local image descriptors into compact codes</a>, to perform image classification. As a ... | g21150 | [
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<p>The help pages for MGCV in R states the following: </p>
<blockquote>
<p>Note that when using factor by variables, centering constraints are
applied to the smooths, which usually means that the by variable
should be included as a parametric term, as well.</p>
</blockquote>
<p>What exactly does this mean? What... | g63464 | [
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-... |
<p>I have some data that I would like to compare with a theoretical distribution for which I know the parameters. How do I plot the empirical pdf against the theoretical pdf? Perhaps I should add that I would like to plot two continuous pdfs.</p>
<p>Edit:</p>
<p>I am sorry if this problem is more related to Stack Ove... | g63465 | [
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<p>I have survival data in which a certain percentage of the failures are known exactly and the rest are currently estimated based on known measurement errors. Should I interval censor the exact measurements as well and proceed with interval censored data or treat some other way.</p> | g63466 | [
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... |
<p>I am new to ML and I'm having trouble figuring out how to implement a Maximum Entropy Markov Model for a sequence labeling task. Given this MEMM equation
$$
P_{s'}(s|,o)=\frac{1}{Z(o,s')}\exp\left(\sum_{a}\lambda_{a}f_{a}(o,s)\right)
$$
Where $s'$ is the previous classification, $s$ is the current classification, a... | g21153 | [
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0.0111... |
<p>If $X_i \overset{i.i.d.}\sim N(\mu, \sigma^2) $, we know that: $\bar{X} \sim N(\mu, \sigma^2 /n)$.</p>
<p>But why does:</p>
<p>$$\exp\left({\sigma^{2}\over 2}\sum_{i=1}^{n}(t_{i}-\bar{t})^{2}\right)= M_{X_{1}-\bar{X},X_{2}-\bar{X},...,X_{n}-\bar{X}}(t_1,t_2,...,t_n)$$</p>
<p>Where $M$ is the moment generating fun... | g63467 | [
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<p>Let's say that you're dealing with a good that has a finite amount of demand that goes down very rapidly over time. Movies at the box office are a good example. They mostly start out at the box office with their opening week as their biggest, and then sales decrease with each subsequent week.</p>
<p>Let's say also ... | g63468 | [
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<p>Imagine a game where an encounter between player and cpu plays like this:</p>
<p>Player has <code>pattack</code> stat, cpu has <code>cdefense</code> stat, and then there's a uniformly random generated variable <code>rnd</code> that, let's say, can have the values in the range -0.2 to +0.2.</p>
<p>The logic is easy... | g63469 | [
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... |
<p>I have 200 training set data with a feature dimension of 1711. I get 50 support vectors; is there a rule of thumb for how many support vectors I should get for N training set data in order for the model to be generalized? Obviously, having 200 support vectors for 200 training set data is bad overfitting. I was wande... | g63470 | [
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<p>Here is a scenario: The average score on an exam in Yamaha Elementry in year 1 is 75.1%. 200 students took that test in year 1. In year 2, the average score was 76.5%, which comprised of 230 students. Based on this information, how significant was the performance from year 1 to year 2. Thank you.</p> | g63471 | [
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<p>I have an experiment that I'll try to abstract here. Imagine I toss three white stones in front of you and ask you to make a judgment about their position. I record a variety of properties of the stones and your response. I do this over a number of subjects. I generate two models. One is that the nearest stone... | g37972 | [
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<p>I am looking for the Hurst exponent calculation methodology. Please suggest online materials / methodology papers.</p> | g63472 | [
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<p>The statistical distance or Mahalanobis distance between two points $x = (x_1,\dots,x_p)'$ and $y = (y_1,\dots,y_p)'$ in the $p$-dimensional space $\mathbb R^p$ is defined as $$d(x, y) = \sqrt{ (x-y)' Q^{-1} (x-y)}$$
Where $Q$ is the covariance matrix that represents the measurement uncertainty of both variables $x$... | g63473 | [
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... |
<p>I am trying to implement a system for automatic document categorization, where each document of a corpus belongs to some class. I define the following contingency table for every class C and every word W:</p>
<p>$\begin{array}{c|cc}
& W & \bar{W}\\
\hline
C & \frac{nb\_docs(C,W)}{nb\_docs} & \frac{... | g40458 | [
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0.013931522145867348,
0.040331095457077026,
0.042... |
<p>I have a regression problem where I would like to predict values given several thousand sparse features. The general data set is an $n \times m$ matrix where each row contains a sample with a value I would like to predict. The remaining columns are features that I want to use to predict the value. What would be a go... | g63474 | [
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0.... |
<p>I have fitted an ARIMA (0,1,1) model with a drift term using the “forecast” package. I want to perform a simulation study to obtain the mean of the forecasted values and the 95% forecasting intervals and compare them with the “Exact” mean and 95 forecasting intervals. The code below is what I have done. The graph s... | g63475 | [
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<p>There are umpteen million research papers regarding relationships between various patient attributes (e.g. how does gene x affect condition y?). What I am interested in though is a distance metric between patients in toto. Sort of like if I were constructing a dating site, I'd want to know how similar two people are... | g63476 | [
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<p>I am interested in discovering motifs in a set of DNA sequence(say 100) and I would like to use the approach of using a subgroup(say 10 from 100) and likewise create random subgroups(picking 10 from 100 randomly) to discover the motifs in the given set of DNA sequences. I would like to know from statistics point of ... | g21163 | [
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0.016395479440689087,
... |
<p>let's say I have n ts (ts_1, ts_2 ...). each ts is non-stationary, normal distributed and may correlated. </p>
<p>I want to use a model to predict the ts and test how good it is doing out of sample and what i use to measure the prediction power is simple mean of error.</p>
<p>To be concrete, i have 100 ts with 105... | g63477 | [
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<p>Given an MA(2) model</p>
<p>$$X_t = e_t + A_1 e_{t-1} + A_2 e_{t-2}$$</p>
<p>There are cases where there are multiple solutions. Given time series data that we can correctly estimate one solution $(A_1^*,A_2^*)$, how would we calculate the other pairs of coefficients satisfying the model from these?</p>
<p>How do... | g63478 | [
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0.0906309187412262,
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0.004489692393690348,
0.08866196125745773,
0.03025... |
<p>The <a href="http://en.wikipedia.org/wiki/Theil%E2%80%93Sen_estimator" rel="nofollow">Theil-Sen estimator</a> is a really nifty algorithm that produces a regression line that is relatively insensitive to outliers <strong>both</strong> in the response variable and the predictor variable. </p>
<p>I've been wondering ... | g63479 | [
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0.0032162030693143606,
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0.03951265662908554,
... |
<p><strong>I would like to discriminate sampled areas that are representative or not representative of their corresponding population, for a given characteristic.</strong></p>
<p>Suppose I have surveyed areas (i.e. Census tracts) within a given population area (i.e. county). I want to compare characteristics of my sam... | g21165 | [
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<p>I am not sure how to do a mediation analysis with my outcome as a factor while mediating and causal variables are continuous. I have tried using the "mediation" package in R for this mediation analysis, but realized that it will not allow me if my outcome is the only factor.
Is there another way to do this? </p>
<p... | g63480 | [
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0.05339384078979492,
0.05208304151892662,
-0.00562871852889657,
-0.052647482603788376,
-0.01280840951949358,
-0.0018037111731246114,
-0.01090952567756176,
0.... |
<p>Is it possible to do k-fold cross-validation to <strong>test</strong> all data, rather than using kfcv to find the optimal hypothesis as is typically done.</p>
<p>Example:</p>
<p>Say I want to use a svms on a dataset of size 1000. Could I use 900 events to train the svm for the testing of the other 100 events. The... | g21166 | [
0.0519065335392952,
0.03518664464354515,
0.02894732356071472,
0.04034736379981041,
-0.026300527155399323,
-0.008667507208883762,
-0.007121335715055466,
0.08909803628921509,
-0.018817126750946045,
-0.0002620396262500435,
0.033533476293087006,
-0.021549280732870102,
0.05618290603160858,
0.03... |
<p>I'm doing a logistic regression and I'm using a model where <em>all</em> included variables are dummy variables (0 or 1). Let's say we have a model with four independent variables and let the constant represent the reference category.</p>
<p><strong>Question:</strong> How do we calculate the marginal effect of one ... | g21167 | [
-0.008640017360448837,
-0.031530264765024185,
0.00939332228153944,
-0.050414640456438065,
0.023519953712821007,
0.015302310697734356,
-0.009602537378668785,
0.066327765583992,
-0.05087337642908096,
-0.005527086555957794,
-0.011407279409468174,
0.07583054900169373,
-0.0072677647694945335,
0... |
<p>I am trying to build a demand forecasting model for human resource team. I have thought of using monte carlo simulation method to do it. Is it the right technique for it? Has anyone used it to forecast human capital? What variables should i take into consideration to develop a model? The variables i can think of are... | g63481 | [
0.018824562430381775,
0.03341620787978172,
0.01833265647292137,
-0.04214964061975479,
-0.02807781472802162,
0.021587340161204338,
0.018740858882665634,
-0.008341647684574127,
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0.022005785256624222,
0.005088547244668007,
0.004027816466987133,
0.056777097284793854,
-0.0... |
<p>I have a file that can be considered as a matrix with each row representing a measurement of gene expression of different samples (each column is a sample). I want to find those genes with the most interesting patterns of expression across samples. That means that several samples have a similar expression range, ano... | g63482 | [
0.004198865033686161,
0.001846417668275535,
-0.015767902135849,
-0.0486689917743206,
-0.008036376908421516,
-0.06971539556980133,
0.028315994888544083,
-0.00007874616858316585,
-0.05480421334505081,
-0.02748163603246212,
0.021285727620124817,
-0.033072344958782196,
0.033037059009075165,
0.... |
<p>If <i>x1, x2,..</i> are identically distributed random variables with given mean, and N is a random variable >= 0 and N is independent of x1,x2,... If <code>y=x_1+x_2+...x_n</code>. How do we find <code>E(y|N=n)</code>?</p>
<p><code>
E(y|N=n) = sum_Y(y*P(Y=y|N=n)) = sum_Y(y*P(Y=y,N=n)/P(N=n))
</code></p>
<p>I am n... | g21172 | [
-0.004059611354023218,
0.012030479498207569,
-0.016450058668851852,
-0.02198849245905876,
0.015771392732858658,
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-0.014522230252623558,
0.014046957716345787,
0.00164966587908566,
0.005604961887001991,
-0.0866302102804184,
0.02362252213060856,
0.03133922815322876,
0.06... |
<p>Under which conditions should we expect the difference-in-difference estimate to be equal to the equivalent panel data model? </p>
<p>Strictly speaking, whenever we have a experiment that offers a well defined treated and control groups in two periods of time, for using difference-in-difference methods, people reco... | g63483 | [
0.0020941414404660463,
-0.030254816636443138,
-0.004649190232157707,
-0.04121166467666626,
0.04689396172761917,
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0.04292401298880577,
0.05716922506690025,
-0.006445982493460178,
-0.020747700706124306,
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0.031407762318849564,
-0.011024323292076588,
... |
<p>I am using ggplot and I would like to label the scales in each facet of a plot manually. The concept is discussed here:</p>
<p><a href="http://groups.google.com/group/ggplot2/browse_thread/thread/d2044ed0f91de98a" rel="nofollow">http://groups.google.com/group/ggplot2/browse_thread/thread/d2044ed0f91de98a</a></p>
<... | g40771 | [
-0.027481021359562874,
0.027740977704524994,
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0.033293966203927994,
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0.011006747372448444,
0.07370015233755112,
0.01741996593773365,
0.01620711013674736,
0.0... |
<p>I'm testing ADF, PP and KPSS unit tests with tseries library. I get strange result with ADF and PP.</p>
<p>I have this vector:</p>
<pre><code>x <- rnorm(1000)
</code></pre>
<p>obviously this vector is trend stationary. OK, I've done ADF, PP and KPSS tests and all of these confirm it.</p>
<p>I have noticed tha... | g21175 | [
0.033205728977918625,
-0.020650379359722137,
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0.0010224853176623583,
0.04011843353509903,
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0.028449805453419685,
0.07022015005350113,
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-0.03892739117145538,
0.020831942558288574,
0.05034378170967102,
0.05581127479672432,
0.012... |
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