question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I have been reading Zuur, Ieno and Smith (2007) Analyzing ecological data, and on page 262, they try to explain how nMDS (non-metric multidimensional scaling) algorithm works. As my background is in biology and not math or statistics per se, I'm having hard time understanding a few points and would ask you if you co... | g45819 | [
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<p>I have a data set with many missing observations for certain parameters (NA values) in it. I have been performing model selection using AIC. Based on AIC scores I have reduce the model to the form</p>
<pre><code>y = a*b + c
</code></pre>
<p>Where <code>a</code>, <code>b</code> and <code>c</code> are continuous dep... | g60313 | [
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<p>This is a favorite of mine</p>
<p><img src="http://i.stack.imgur.com/WD3k3.png" alt="A rendition of a favorite graph of mine"></p>
<p>This example is in a humorous vein (credit goes to a former professor of mine, Steven Gortmaker), but I am also interested in graphs that you feel beautifully capture and communicat... | g60314 | [
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<p>I want to do a multiple imputation of missing data using SPSS. I have a nominal (categorical) variable X with <strong>missing values</strong> codified as '9' and <strong>not applicable</strong> values codified as '8'.</p>
<p>How can I constrain imputed values to X, for not imputing '8' (not applicable) to a '9' (mi... | g60315 | [
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<p>Specifically, when I add "newdata":</p>
<pre><code>> predict(pca,newdata=EODPositions[rr,])
PC1 PC2 PC3 PC4 PC5 PC6 PC7 PC8 PC9 PC10 PC11 PC12 PC13 PC14 PC15 PC16
[1,] -7.542401 9.356362 -26.73124 -51.57566 2.645592 68.61375 -12... | g60316 | [
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<p>The regular linear regression model is easy to present; we are minimizing the sum of the least square errors: $$\sum_{i=1}^{n} ( y_i - \hat{y}_i)^2$$</p>
<p>How do we present the mixed model? More specifically, we are wondering about how to present the following simple model:</p>
<pre><code>lmefit = lmer(MathAch ... | g60317 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/5450/what-if-interaction-wipes-out-my-direct-effects-in-regression">What if interaction wipes out my direct effects in regression?</a> </p>
</blockquote>
<p>I am just wondering why would adding an interact... | g49395 | [
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<p>$R = S + xx^t$</p>
<p>where $x \in \mathbb{R}^n$ and $R$ and $S$ are $n \times n$ covariance matrices. </p>
<p>Is there anything I can say about the eigenvectors of $R$ and $S$? Or at least the largest eigenvalue and eigenvector pair of R?</p>
<p>Is there a way to express the eigenvectors of $R$ in terms of $S$... | g16360 | [
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<p>I have data with a starting (y) value that sequentially increments/decrements as (x) time measured in days passes.
I found this link for creating a linear regression of the data
<a href="http://www.easycalculation.com/statistics/regression.php" rel="nofollow">http://www.easycalculation.com/statistics/regression.p... | g45840 | [
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<p>Well we've got favourite statistics quotes. What about statistics jokes?</p>
<p>So, what's your favourite statistics joke?</p> | g60318 | [
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<p>How can I compute the error on the interquartile range of a sample? By error I mean its std deviation (e.g. error on the mean = RMS/sqrt(N)).</p>
<p>The sample is from a unimodal distribution, similar to normal distribution, but with asymmetric tails.</p> | g27775 | [
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<p>Suppose in time series you have the data in a recent period and you would like to use that data to extrapolate backward to get estimates of the time series back in time. What do you call that? ? Extrapolating forward is forecast, so hindcast?</p> | g16364 | [
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<p>In my model, there are 3 players, whose income is function of two arbitrary parameters. Say, <code>P(1) = F(a,b) where 0<a<1 , 0<b<1 and P(1) is income of player 1</code>. Similarly for other two players we have, <code>P(2)=G(a,b) and P(3)=H(a,b)</code>. Functions F(), G() and H() are known. I have 2 que... | g60319 | [
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<p>I noted that regression task in machine learning is somehow related to solving differential equations approximately - both are trying to approximate unknown function. </p>
<p>Then, my question is: Can ML be somehow helpful in solving differential equations?</p>
<p>Thank you in advance.</p> | g60320 | [
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<p><strong>Context:</strong> I am faced with what I believe is a non-trivial modelling problem that I have been assigned as part of my post-doc. My expertise is in the area of graph / network theory so I have found myself struggling with all the available modelling options and language.</p>
<p><strong>The problem is a... | g60321 | [
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<p>I have some issues with an exploratory factor analysis.</p>
<p>Can anybody please tell me how to calculate the Average Variance Extracted (AVE) and the Composite Reliability from two factors, each with three items using SPSS? If not with SPSS, Stata might help too.</p> | g38213 | [
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<p>UPDATE: caret now uses <code>foreach</code> internally, so this question is no longer really relevant. If you can register a working parallel backend for <code>foreach</code>, caret will use it.</p>
<hr>
<p>I have the <a href="http://caret.r-forge.r-project.org/Classification_and_Regression_Training.html" rel="no... | g60322 | [
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<p>I'm comparing scores for two small groups of individuals that competed in a tournament, and I'm being told that the comparison calls for a Mann-Whitney U test. It feels wrong to me, though: my two sets of scores are fundamentally interdependent because the two groups competed against one another.</p>
<p>Briefly: I ... | g60323 | [
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<p>Suppose I wanted to fit a model of the form
$$y_i = \beta_0 + \sum_{1 \le j \le k} \beta_j X_{i,j} + \gamma_i Z_i + \epsilon_i,$$
to some data, where the regressors $X$ and $Z$, and the regressand $y$ are observed, and where $\gamma_i$ is a Bernoulli random variable that equals one with (unknown) probability $p$ and... | g45855 | [
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<p>I want to transpose a data frame in R with <code>unstack</code>. Consider the two data frames, <code>a</code> and <code>b</code>:</p>
<pre><code>> a
count state
1 199665 RSTO
2 4147 RSTR
3 31274 S1
4 1 S2
5 2522 S3
6 118009 SF
> b
count state
1 31956 RSTO
2 11689 RSTR
3 670... | g60324 | [
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<p>Let's say I have a function to simulate data for negative binomial regression: </p>
<pre><code>simnegbin = function(X, beta, alpha) {
lambda = exp(1 + X %*% beta)
y=NULL
for (j in 1:length(lambda)) y = c(y,rnbinom(1,mu = lambda[j],size = alpha))
return(y)
}
</code></pre>
<p>And I call that function like this:</p>
... | g60325 | [
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<p>Suppose we are building a DBN (Deep Belief Network) and we have already trained some lower layers as Restricted Bolzmann Machines.
Now we add a new layer, with new weights and new biases for the new hidden nodes.</p>
<p>Do we use the biases of the hidden nodes of the previous layer as the biases of the 'visible' no... | g60326 | [
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<p>I am using libsvm for a 2-class classification problem. For my testing I use the C-SVM with RBF kernel.</p>
<p>My main problem seems to be that the classes are highly imbalanced. While I have 35000 datasets in the -1 class, there are only 16 datasets in the +1 class (roughly 0,05%) n the training data. That should ... | g60327 | [
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<p>I have an equation to predict the weight of manatees from their age, in days (dias, in portuguese):</p>
<pre><code>R <- function(a, b, c, dias) c + a*(1 - exp(-b*dias))
</code></pre>
<p>I have modelled it in R, using nls(), and got this graphic:</p>
<p><img src="http://i.stack.imgur.com/4s1QF.png" alt="enter i... | g60328 | [
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<p>First CV post but prior S.O. user. Thanks for your patience as 'stats' is not my natural habitat. </p>
<p>I have data in the following form, in which I am trying to see if there is a relationship.</p>
<ul>
<li>Daily log returns for a series of companies.</li>
<li>Daily data that may influence the performance of th... | g60329 | [
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<p>I have a dataset with un-even variance and un-equal class sizes (This was a random sample of land cover classes). After using ANOVA to determine significant differences exist among classes, I ran Dunnetts T3. However, I read that Dunnett's T3 should be used for comparing classes to a control, which I do not have. Is... | g60330 | [
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<p>I have to conduct a meta-analysis. Following problem occured: a single study have measured Quality of Life and therefore, used two questionnaires. Now is my question whether I have two choose one of the instrument to include in meta-analysis or is there a possibility to combine the means of the two scales to provide... | g60331 | [
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<p>I am learning about Bayes theorem in machine learning .</p>
<p>$p(h/D) = \frac{p(D/h)p(h)}{p(D)}$</p>
<p>$p(h) = $prior probability of hypothesis h</p>
<p>$p(D)$ = prior probability of training data D</p>
<p>$p(h/D)$ = probability of h given D</p>
<p>$p(D/h)$ = probability of D given h</p>
<p>I am from mathem... | g60332 | [
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<p>I am doing my master's thesis and I must compare various forecasting techniques at different frequencies of datasets. I am using my universities dataset, the REDD dataset, UCI dataset and CER Ireland dataset for this purpose. The data I use is in seconds for a time span of a month and this gives > 3 million records.... | g60333 | [
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<p>I am conducting my confirmatory factor analysis (CFA) using AMOS, and respectivelly get the factor weights, the model fit, etc. However, is there a way in AMOS to export the actual factor scores for each observation into SPSS, and then to use them into the regression model? </p>
<p>Thanks <_></p> | g60334 | [
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-0.028629643842577934,
0.011759796179831028,
0.0005065081059001386,
0.06971579790115356,
-0.0... |
<p>When implementing some NLP project, such as text segmentation, Name Entity Recognition, does using trigram guarantee to perform more accurately than bigram? </p>
<p>$$
Trigram: p(s_t\mid s_{t-2}, s_{t-1})
$$
$$
Bigram: p(s_t\mid s_{t-1})
$$</p>
<p>EDIT: I was using an HMM to do NER on citation records(publications... | g60335 | [
0.014770995825529099,
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0.02204262651503086,
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0.02177252434194088,
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0.0016900083282962441,
0.020829491317272186,
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<p>I m using logistic regression and I am trying to figure out if there is anyway to compute the p-values either in Octave or in Python.
thanks</p> | g60336 | [
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0.042... |
<p>In going over some example problems from class notes, I came across the following problem:</p>
<p>"Suppose we have a regression model $y=\beta_0+\beta_1x_1+\beta_2x_2+\beta_3x_4+\beta_4x_4+\epsilon$. We wish to test the null hypothesis that $H_0: \beta_1=\beta_2$. Express the hypothesis in terms of $A\beta=c$, prov... | g20834 | [
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0.01314... |
<p>I have two time series</p>
<ul>
<li>$p_t$, the daily market price of a particular kind of good</li>
<li>$f_t$, the daily production of such good</li>
</ul>
<p>Now assume that there is a unique relationship that tells you the optimal production given a price (a supply function):</p>
<p>$q(p_t) = a + b p_t$.</p>
<... | g60337 | [
0.0011306667001917958,
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0... |
<p>I did an experiment across four weeks to collect data on different dependent variables to answer diverse sub-questions. Since on each dependent variable, different participants did not show up and thus I have different missing data from different participants.
Should I remove all different participants' data on dif... | g16374 | [
0.04925866052508354,
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0.002902036067098379,
0.04441231116652489,
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0.016... |
<p>I am modeling my data with ARIMA and to check if my model is good I have to compute the residuals and plot the correlation function and partial correlation function of the residuals. If the results of the functions are between $1.96 \pm 1/\sqrt(\sigma)$ that means that the residuals are drawn from Gaussian process, ... | g60338 | [
0.05496630072593689,
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0.024591034278273582,
0.012196728028357029,
0.04529930278658867,
0.042844392359256744,
-0.0... |
<p>I am carrying out a difference in difference estimation. Regarding control variables addition I am kinda confused. Am I to add control variables which affect the dependent variable or control variables which affect the dependent variable but would not affect the policy effect on the dependent variable.</p> | g60339 | [
0.0023728860542178154,
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0.014551245607435703,
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0.... |
<p>I want to test the effect of reward types (IV) on the motivational factors (DV), in that I want to identify the effect of each type of reward on the level of a moderator. I am using gender as the moderator. I do that by entering each type of reward once in the regression analysis. I have centered the IV, and as the ... | g646 | [
-0.0002561357105150819,
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0.019325098022818565,
0.012202291749417782,
... |
<p>I am trying to apply the method proposed by Chib in Marginal Likelihood from the Metropolis Hastings output to calculate the marginal likelihood of a logit model the includes latent variables. Specifically,
$Pr(Y=1)=\exp\frac{\beta x+z}{1+\exp(\beta x + z)}$
where an unobserved variable $z \sim N(0,\sigma)$.
I wil... | g60340 | [
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0.019780533388257027,
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0.05941859260201454,
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... |
<p>SPSS offers several methods of factor extraction:</p>
<ol>
<li>Principal components (which isn't factor analysis at all)</li>
<li>Unweighted least squares</li>
<li>Generalized least squares</li>
<li>Maximum Likelihood</li>
<li>Principal Axis</li>
<li>Alpha factoring</li>
<li>Image factoring</li>
</ol>
<p>Ignoring ... | g60341 | [
0.04979616403579712,
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0.022309888154268265,
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0.03861969709396362,
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0.039936408400535583,
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0.051650699228048325,
-0.... |
<p>I am wondering if there is any way of doing an intraclass correlation, two-way, mixed, with non-normal data (in this case a ceiling effect)? Alternatively, what the interpretation (if any) would be?</p>
<p>My skewness is -2, and the intraclass correlation is .132. I'm using SPSS to run the analysis. </p> | g60342 | [
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0.04352952912449837,
0.011201397515833378,
0.006750556640326977,
0.02... |
<p>I have this formula:</p>
<p>$\Delta a_{ki} \propto v_k (v_i - \langle v_i \rangle_{recon})$</p>
<p>First, what does $\propto$ mean and second, what is the difference between $v_i$ and $\langle v_i \rangle$? </p> | g60343 | [
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0.04412325099110603,
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<p>I have a dataset for which I have multiple sets of binary labels. For each set of labels, I train a classifier, evaluating it by cross-validation.</p>
<p>I want to reduce dimensionality using PCA. My question is:</p>
<p><strong>Is it possible to do the PCA once for the dataset and then use this new dataset as desc... | g60344 | [
-0.016012893989682198,
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0.03543153032660484,
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-0.018233299255371094,
0.022196218371391296,
0.044831689447164536,
0.016016755253076553,
0.0338... |
<p>I am struggling with the interpretation of the AFT model, Cox proportional hazard model and discrete-time hazard model.</p>
<p><em>My question is:</em></p>
<p>Can the <strong>coefficients in discrete-time hazard model</strong> also be interpreted (e.g. by using <code>glm</code> or <code>glmer</code> in <code>R</co... | g16381 | [
0.03665332868695259,
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0.0014845808036625385,
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0.06924369931221008,
0.020327724516391754,
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0.05223900079727173,
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0.010360692627727985,
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0.11659597605466843,
-0.... |
<p>I thought I was good at statistics until I found myself drowning in a simple problem that I have difficulty solving, hence my appeal for your expertise :)</p>
<p>1) A test has been administered to many candidates.</p>
<p>2) The number of candidates is >20,000. c1,c2,c3 ...C20000+</p>
<p>3) Each candidate has been... | g60345 | [
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0.010762100107967854,
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0.07338939607143402,
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0.0018022159347310662,
0.0632597804069519,
-0.02... |
<p>I have 2 arrays with data about the field pattern around antennae in them. I want to find how similar they are. Does this mean I need to find the covariance matrix or the correlation coefficients of the matrix?</p>
<p>The data in the arrays looks like this (made up values):</p>
<pre><code>Radius(m) Angle(deg) ... | g60346 | [
0.004315237049013376,
-0.04624099284410477,
0.001984768081456423,
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0.023466678336262703,
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0.051647450774908066,
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-0.023918461054563522,
-0.05557233840227127,
0.049882855266332626,
-0.018946409225463867,
-... |
<p>I have data where different reviewers rated how important multiple topics are on a scale of 1 to 5 (Likert scale). Each of the topics is assigned to a group. I want to see if there any differences in the overall rating of importance between the groups of topics.</p>
<p>Here is an example of what the data looks like... | g16383 | [
-0.017166975885629654,
-0.005936410743743181,
-0.013953021727502346,
-0.061216019093990326,
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0.017010288313031197,
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-0.07637303322553635,
0.04444712772965431,
0.049643367528915405,
-0.023272931575775146,
0.009643240831792355,... |
<p>I have the regular hypothesis where I'm testing whether the mean of one variable is larger than the mean of the other variable or not:</p>
<pre><code>H0: mean(variable1) <= mean(variable2)
H1: mean(variable1) > mean(variable2)
</code></pre>
<p>I've ran the Welch's test variation of the student t test in R an... | g16384 | [
-0.013802786357700825,
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0.013768833130598068,
0.06874509900808334,
0.044579535722732544,
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-0.02378256991505623,
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0.0390164777636528,
0.02333744987845421,
0.... |
<p>I am attempting to analyze some data that includes 10 repeated measurements on 10 different samples. This would normally require using mixed models, and I have attempted to model these using <code>lme</code> in <a href="http://cran.r-project.org/web/packages/nlme/index.html" rel="nofollow">nlme</a> and using <code>... | g16385 | [
0.010739704594016075,
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0.04010486975312233,
0.008961759507656097,
0.04662289097905159,
0.005642682779580355,
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0.03645476698875427,
0.0... |
<p>I would like to decompose the following time series data into seasonal, trend, and residual componenets. The data is an hourly Cooling Energy Profile from a commercial building:</p>
<pre><code>TotalCoolingForDecompose.ts <- ts(TotalCoolingForDecompose, start=c(2012,3,18), freq=8765.81)
plot(TotalCoolingForDecomp... | g37689 | [
0.009401347488164902,
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0.04175799340009689,
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0.04330392926931381,... |
<p>I am looking for a statistical software package which I can use in an introductory course of statistics for a social science study programme. The students have no prior knowledge of statistics and no experience with programming languages either. The goal is to introduce them to basic statistical concepts (as means, ... | g60347 | [
0.025067729875445366,
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-0.036786530166864395,
0.07359511405229568,
0.019216757267713547,
0.07105565816164017,
... |
<p>I want to fit a hyperbolid distribution according to my notation:</p>
<p>\begin{align*}
H(l;\alpha,\beta,\mu,\delta)&=\frac{\sqrt{\alpha^2-\beta^2}}{2\alpha \delta K_1 (\delta\sqrt{\alpha^2-\beta^2})} exp\left(-\alpha\sqrt{\delta^2+(l-\mu)^2}+\beta(l-\mu)\right)
\end{align*}</p>
<p>I use the HyperblicDistr pac... | g60348 | [
0.07088854163885117,
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0.05014610290527344,
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0.04025997966527939,
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0.02108539082109928,
0.0338485985994339,
0.001407... |
<p>I'm a complete noob when it comes to statistics, so please excuse my lack of standard terminology. I think my question might be related to normalization, but please re-tag if I'm wrong. </p>
<p>I'm a programmer by trade, and I've been tasked with creating a chart which shows how the number of errors in a data set c... | g37481 | [
0.02046922966837883,
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0.0016963211819529533,
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0.0... |
<p>I'm using Doronix Math Toolbox. They have statistical functions (<a href="http://www.doronix.com/statistics.html" rel="nofollow">http://www.doronix.com/statistics.html</a>). I can't figure out how they are finding p-value in ranksum and signsum tests. Does anyone know it? I'm asking because answer is different than ... | g60349 | [
-0.008598599582910538,
0.0028207157738506794,
-0.023391857743263245,
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0.05101010948419571,
0.05317869409918785,
... |
<p>I have a three level contingency table, with count data for several species, the host plant from which they were collected and whether that collection happened on a rainy day (this actually matters!). Using R, fake data might be something like this:</p>
<pre><code>count <- rpois(8, 10)
species <- rep(c("a... | g60350 | [
0.03390909358859062,
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0.030979985371232033,
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0.0018312480533495545,
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0.04175245761871338,
0.030334021896123886,
... |
<p>Can I manually include lag dependent variable among explanatory variables on panel data model estimations( in trying to establish relationship between gross profit/earning before interest and tax as dependent variable for equations 1&2 repectively. Raw material, work in progress, finish good inventories are the ... | g34582 | [
0.011724080890417099,
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0.04534861072897911,
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-0.03722241520881653,
0.0010633277706801891,
0.05017872154712677,
0.021264532580971718,
0... |
<p><strong>Update: I wanted to clarify that this is a simulation. Sorry if I confused everyone. I have also used meaningful names for my variables.</strong></p>
<p>I am not a statistician so please correct me if I make a blunder in explaining what I want. In regard to my <a href="http://stats.stackexchange.com/questio... | g16389 | [
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0.0... |
<p>While attending conferences, there has been a bit of a push by advocates of Bayesian statistics for assessing the results of experiments. It is vaunted as both more sensitive, appropriate, and selective towards genuine findings (fewer false positives) than frequentist statistics.</p>
<p>I have explored the topic s... | g588 | [
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0.011763717979192734,
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0.059997331351041794,
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0.... |
<p>I have a short question. I've performed a principal component analysis and obtained two components. Are two components enough two perform a cluster analysis (number of participants > 400)?
Thanks for your help!</p> | g60351 | [
0.0004960402147844434,
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0.004709460772573948,
0.0005043619894422591,
0.05945334956049919,
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... |
<p>I am trying to understand how influence functions work. Could someone explain in the context of a simple OLS regression</p>
<p>\begin{equation}
y_i = \alpha + \beta \cdot x_i + \varepsilon_i
\end{equation}</p>
<p>where I want the <a href="http://en.wikipedia.org/wiki/Robust_statistics#Empirical_influence_function"... | g60352 | [
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0.06809747964143753,
0.09744508564472198,
-0.02... |
<p>I have a rainfall data consisting of around 95 years for the rows and twelve months of the year for columns. So this is a 95x12 matrix, not a column vector. Can I derive any idea about the months to be concentrated in view of rainfall with principal components analysis? If so what would the principal components refe... | g60353 | [
0.015428480692207813,
-0.03130165487527847,
0.008245853707194328,
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<p>I have a constant problem understanding SVM for both linear and non-linear separable cases. I understand upto a point that SVM establishes a hyperplane that has the maximum or optimal distance between the two classes to be separated, which basically serves as the decision boundary at the time of prediction. I have f... | g60354 | [
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<p>i try to perform some k nearest neighbor classification in R.
That for i want to select the most meaningful features to deal with the curse of dimensionality.
I have already decided to use Mahalanobis distance and euclidian distance.
My question now is, what may be the best way to select the features to use. As i ha... | g16395 | [
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<p>I am measuring two continuous variables ($X,Y$) for 21 subjects. $X$ and $Y$ have 216 data points each (per subject). I would like to see if $X$ and $Y$ are correlated at the group level. I can think of 3 options:</p>
<p>a) Concatenate all the subjects together and compute the correlation. I believe this method wil... | g60355 | [
0.0484849251806736,
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<p>I have two ordinal variables which are set on different scales. The variables were extracted from a questionnaire. The first variable ranges from -12 to +12 with a step of 1 width, ( -12, -11,...-2,-1 , 0, 1, 2,..., +11, +12) and the second one ranges only from -2 to +2 with the same step width(-2,-1,0,+1,+2). I wo... | g60356 | [
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<p>I would like to model the performance of a rainwater tank, which has a stochastic input (rainfall). The data are the empty volume in the tank at the end of each day. The values are skewed towards the extremes, and I am not sure how to model this or present it statistically. Reviewing various distributions in Wikiped... | g60357 | [
-0.017843153327703476,
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<p>What is the minimum length of a time-series for considering the results of the Mann-Kendall trend test "coherent"?</p> | g48684 | [
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<p>I've been reading Tukey's book "Exploratory Data Analysis". Being written in 1977, the book emphasizes paper/pencil methods. Is there a more 'modern' successor which takes into account that we can now instantaneosly plot large data sets? </p> | g60358 | [
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<p>I am working on fitting a Cox model to predict. But several predictors violated the proportional hazards assumption. I am gonna to do stratified Cox model to adjust them. But the results of stratified Cox model would not include any information or influence of those stratified predictors. As I really want to see the... | g45894 | [
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<p>Imagine the following common design:</p>
<ul>
<li>100 participants are randomly allocated to either a treatment or a control group</li>
<li>the dependent variable is numeric and measured pre- and post- treatment</li>
</ul>
<p>Three obvious options for analysing such data are:</p>
<ul>
<li>Test the group by time i... | g49500 | [
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<p>Given an experiment where a number of entities are measured/evaluated using two different methods in two different runs, how would one go about calculating the correlation between the runs? </p>
<p>In other words; I have about a thousand entities $X_i$ each with two scores $S_{i,1}$ and $S_{i,2}$, and two such data... | g60359 | [
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<ol>
<li>Incremental clustering algorithms</li>
<li>Online clustering algorithms</li>
<li>Data stream clustering algorithms</li>
<li>Single pass clustering algorithms</li>
</ol>
<p>Are the following expressions related? Does some of them include others? What is the difference between them? What are the constraints tha... | g49797 | [
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<p>I have a model file that was created using svmlight in classification mode with a linear kernel. Is it possible to convert this file so that libsvm can use it for classifying?</p> | g60360 | [
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<p>I am running a regression with several independent variables with 32 observations (from 1975 to 2006 and they are yearly data). The issue here is that there does not exist any observation for one of the variables prior to 1980. Consequently, that variable has 5 missing observations (from 1975 to 1979).
Is there any ... | g16405 | [
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0.048... |
<p>What methods are there for measuring the strength of arbitrary, highly non-linear relationships between two paired variables? By highly non-linear, I mean relationships that can't sensibly or reliably be modelled by regression to a known model. I'm particularly interested in time-series, but I imagine any thing that... | g16407 | [
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<p>Consider linear regression with some regularization:
E.g. Find $x$ that minimizes $||Ax - b||^2+\lambda||x||_1$</p>
<p>Usually, columns of A are standardized to have zero mean and unit norm, while $b$ is centered to have zero mean. I want to make sure if my understanding of the reason for standardizing and centerin... | g48685 | [
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<p>I have been presented with a dataset comprised of individuals and the number of teeth they have had extracted. The maximum is 32, and almost half of the data are zeros. I have been asked to suggest an appropriate multivariate model for these data.</p>
<p>I originally thought this would be a negative binomial distri... | g16408 | [
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... |
<p>I've been reading Wagenmakers (2007) <a href="http://www.brainlife.org/reprint/2007/Wagenmakers_EJ071000.pdf" rel="nofollow">A practical solution to the pervasive problem of p values</a>. I'm intrigued by the conversion of BIC values into Bayes factors and probabilities. However, so far I don't have a good grasp of ... | g60361 | [
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<p>I am attempting to build a simple multiple regression in order to estimate the value of a home. The 5 datapoints are 5 comparable home sales (similar in size, lot, location, # of bedrooms, etc...).</p>
<p>If you run such a model, the software will say you need one more datapoint than variables. </p>
<p>So, how a... | g45910 | [
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0... |
<p>As more and more data (e.g., Census, health, labor) becomes available with outcomes at the household-level on randomly selected households each year (or every other year) that can be paired with geographic data (e.g., regional economic conditions, state or local policy choices or housing prices, etc.), we need to bu... | g60362 | [
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0.013444535434246063,
0.0362611785531044,
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0... |
<p>Given coefficients from an arima model, how do you calculate the "fitted value" for the first observation of the series?</p>
<p>For example, given the data (called xshort):</p>
<p><img src="http://i.stack.imgur.com/ZvdWs.jpg" alt="enter image description here"></p>
<p>and a call to R:</p>
<pre><code>mod<-Arim... | g60363 | [
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0.037983488291502,
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0.01100322138518095,
0.012571628205478191,
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0.026256157085299492,
-0.05991391837596893,
0.07600957900285721,
0.09786585718393326,
0.00385... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/7948/when-is-it-ok-to-remove-the-intercept-in-lm">When is it ok to remove the intercept in lm()?</a> </p>
</blockquote>
<p>When shall I include an intercept in linear regression?</p>
<p>Hi all,</p>
<p>In... | g49302 | [
0.054126061499118805,
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0.011073851957917213,
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0.014928673394024372,
0.0550142340362072,
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-... |
<p>I had a quick question about the Peru LSMS from 1994 (<a href="http://microdata.worldbank.org/index.php/catalog/617" rel="nofollow">http://microdata.worldbank.org/index.php/catalog/617</a>). The LSMS is split up into several dozen files, all of which contain different pieces of information (some of them contain info... | g60364 | [
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0.020469870418310165,
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0.007873939350247383,
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-... |
<p>I was wondering about this, especially because I was checking this thing called "clarify" which apparently does some montecarlo simulations, but I don't understand very well if it serves my purpose (assesing goodness of fit). Greetings and thanks so much. </p> | g45916 | [
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<p>I have a series of data of photon counts versus time. These data are periodic, then I can fold them and obtain an average profile of the data. Nonetheless, some variations appear sometime in the single profiles. To check if the average profile and the single ones are statistically different, they suggested me to use... | g60365 | [
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0.05703336000442505,
0.05329066514968872,
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0.02360289916396141,
0.0007382803596556187,
0.03261174261569977,
-0.0029479253571480513,
0.02... |
<p>I have a dataset with 3000 sub-regions with data about their population by income range and their value spending in a commodity. I made a OLS model with log-log transformation using <code>lm()</code> function in R to predict the spending in another 300 sub-regions.</p>
<p>$$
\ln(Y+1) = \beta_0 + \beta_1\ln(X_1+1) +... | g60366 | [
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0.034574929624795914,
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-0.03284614533185959,
-0.045720670372247696,
0.04789528250694275,
0.07059995830059052,
... |
<p>I have a sample set of values that were taken over a period of time. However, the delta time between each sample is different.</p>
<p>Do I need to account for the different time deltas in the std-dev?</p>
<p>Is std-dev even appropriate for this kind of data?</p>
<p><hr>
More info...</p>
<p>The data are temperatu... | g24134 | [
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0.... |
<p>I have to analyze a factorial design with five factors (one of them nested in another one) and numeric responses. I would like to perform a nonparametric ANOVA, but of course I can't use neither Kruskall Wallis nor Friedman test (I have replicated measures). Is there a command or a code in R that could help me?
Than... | g16416 | [
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0.02677455171942711... |
<p>Suppose we need to take an action on a population with income (x) more than $5,000. Income is not observed directly.</p>
<p>Should we use logistic regression to estimate x, or should we use logistic regression to estimate the probability of x>5000 directly? (What are the drawbacks/advantage of the methods?)</p>
<p... | g60367 | [
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0.00347763579338789,
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0.0437... |
<p>I'm trying to evaluate a path dependent function, $f(r_t)$, on a Cox-Ingersoll-Ross process:</p>
<p>$dr_t = \theta (\mu - r_t)dt + \sigma \sqrt r_t dW_t$</p>
<p>by Monte Carlo simulation.</p>
<p>Could anyone suggest and explain any effective variance reduction techniques that could be used on this process? E.g. ... | g45920 | [
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... |
<p>Can somebody explain what is the natural interpretation for LDA hyperparameters? <code>ALPHA</code> and <code>BETA</code> are parameters of Dirichlet distributions for (per document) topic and (per topic) word distributions respectively. However can someone explain what it means to choose larger values of these hype... | g45012 | [
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<p>I like to tinker in my spare time with clustering algorithms.</p>
<p>Over the past few days I was attempting to tinker with a clustering algorithm using density fields of the data.</p>
<p>I tried several variations and I was surprised that my algorithms were reasonably stable and robust.</p>
<p>I want to continue... | g60368 | [
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0.010437938384711742,
-0.0449661947786808,
0.01309353206306696,
-0.026069683954119682,
0.005576919298619032,
0.005471815355122089,
0.025296857580542564,
-0.03776480257511139,
0.09261468052864075,
-0.00081... |
<ol>
<li>Model<br>
The firm and enforcement agency interact in more than one domain. This may arise because a single agency is responsible for enforcing more than one regulation or because it enforces the same regulation at more than one constituent plant of a multi-plant firm.
For simplicity we will assume that the nu... | g60369 | [
0.018359338864684105,
0.02343425713479519,
-0.0010802469914779067,
0.046910881996154785,
0.06201986223459244,
-0.031922996044158936,
0.08872497826814651,
0.053021203726530075,
-0.0025121269281953573,
-0.013902489095926285,
-0.013964985497295856,
0.015854770317673683,
0.030554093420505524,
... |
<p>I am working in an extremely memory constrained environment, and the number of support vectors my Matlab design is generating is just not something that scales. That led me to move to finding a way to lower the number of support vectors. And I came across this paper from MIT: <a href="http://dspace.mit.edu/handle/17... | g60370 | [
0.038050297647714615,
-0.022077875211834908,
0.008348643779754639,
-0.02735838294029236,
-0.012876506894826889,
-0.04874712973833084,
-0.010866107419133186,
0.05321948975324631,
-0.08421030640602112,
-0.014267482794821262,
-0.007583172991871834,
-0.044910382479429245,
0.050663869827985764,
... |
<p>I have some data and I would like to test the hypothesis that they come from a homogeneous Poisson process. I can of course look at the inter event times and test if these are exponentially distributed. However this misses lots of reasons why it might not be Poisson it seems . Is there a list of tests, or a particu... | g60371 | [
0.025138653814792633,
0.02425430715084076,
-0.0009511134121567011,
-0.06159694492816925,
0.016562309116125107,
-0.012924984097480774,
0.005322054028511047,
0.0028304376173764467,
-0.016886288300156593,
-0.02581746317446232,
0.006970980670303106,
0.0348171629011631,
-0.013097011484205723,
0... |
<p>I have a random variable $X(a) = \log(a)$ where a is normal distributed $\mathcal N(\mu,\sigma^2)$. What can I say about $E(X)$ and $Var(X)$? An approximation would be helpful too.</p> | g60372 | [
-0.010779530741274357,
-0.058836739510297775,
-0.03292028605937958,
-0.07472677528858185,
0.003173873294144869,
-0.013299803249537945,
0.027530115097761154,
-0.031601596623659134,
0.009612377732992172,
0.006814923603087664,
-0.018823828548192978,
0.06778309494256973,
0.014880324713885784,
... |
<p>Suppose I have a contigency table</p>
<pre><code> 18 2
3 40
</code></pre>
<p>If I collect more data, it is likely that I obtain a matrix like this</p>
<pre><code>180 20
30 400
</code></pre>
<p>The pvalue drops from 9*10e-11 to 5*10e-100.</p>
<p>By intuition, I think this is because, the more data y... | g16427 | [
0.01942487433552742,
0.006655721925199032,
-0.02305588684976101,
-0.055638380348682404,
0.035817209631204605,
-0.02590864896774292,
0.04256318137049675,
0.0007119851652532816,
-0.052128251641988754,
-0.022059516981244087,
0.013148829340934753,
0.014827858656644821,
0.033021554350852966,
0.... |
<p>I am trying to understand the meaning of the null distribution in Fisher Exact Test.</p>
<p>Suppose I have a contigency table:</p>
<pre><code> Stat1 Stat2
Group1 18 2
Group2 3 40
</code></pre>
<p>If I want to know if <code>Stat1</code> is <em>enriched</em> significantly in <code>Group... | g60373 | [
0.0020300550386309624,
0.007629580330103636,
-0.006037503480911255,
-0.07097368687391281,
0.05403260514140129,
-0.0227117408066988,
0.002257848624140024,
0.035694487392902374,
-0.05058087781071663,
-0.03426896408200264,
-0.022455988451838493,
0.026511365547776222,
0.02571774460375309,
0.01... |
<p>For regression analysis, it is often useful to know the data generating process to check how the used method works. While it is fairly simple to do this for a simple linear regression, this is not the case when the dependent variable has to follow a specific distribution. </p>
<p>Consider a simple linear regression... | g60374 | [
-0.009253425523638725,
-0.051994018256664276,
-0.002420324133709073,
-0.03428751975297928,
-0.025530096143484116,
-0.017875058576464653,
0.009904701262712479,
0.008897265419363976,
-0.02459566853940487,
-0.05012403428554535,
-0.000922330014873296,
0.02401016280055046,
0.05999414250254631,
... |
<p>I want to generate 2 continuous random variables Q1, Q2 (quantitative traits) and 2 binary random variables Z1, Z2 (binary traits) with given pairwise correlations between all possible pairs of them.
Say (Q1,Q2):0.23, (Q1,Z1):0.55, (Q1,Z2):0.45, (Q2,Z1):0.4, (Q2,Z2):0.5, (Z1,Z2): 0.47 </p>
<p>Please help me generat... | g60375 | [
0.04753029718995094,
-0.04816706106066704,
0.006329463794827461,
0.014168445020914078,
0.0006729321903549135,
-0.011385325342416763,
-0.0043715741485357285,
0.02691160887479782,
-0.025979897007346153,
-0.026874642819166183,
-0.0008620849694125354,
-0.0021843155845999718,
-0.06906083971261978... |
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