question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I want to cluster a set of 512 time series.
The time series have sampling intervals of 1 day over a time period of 5 years. Thus, each time series consists of about 1800 samples.
However, many of the samples are zero.
So, my question is: Is it ok to aggregate the samples to larger sampling intervals, e.g. days or ev... | g60429 | [
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<p>I need to perform model selection using a standard p-value approach. Using logistic regression we would like to compare the following models:</p>
<pre><code>Y = A + B + C + D
Y = A*B + A + B + C + D
Y = A*C + A + B + C + D
Y = A*D + A + B + C + D
</code></pre>
<p>I performed the following analysis in R:</p>
... | g60430 | [
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<p>This relates to a previous question of mine which didn't gain many responses, perhaps because it wasn't very clear nd well written. I hope this time I will be more accurate and get your much appreciated assistance.</p>
<p>I am analyzing results of a biological experiment. The results given as a single value ( non-n... | g60431 | [
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<p>I have a process which writes statistics from a server system to a file each second in this format:</p>
<pre><code>label1 label2 label3
344 666 787
344 849 344
939 994 344
</code></pre>
<p>There are a number of different values which I need graphs for, and each value is added to the bottom of the file each second.... | g46062 | [
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<p>I recently read Skillicorn's book on matrix decompositions, and was a bit disappointed, as it was targeted to an undergraduate audience. I would like to compile (for myself and others) a short bibliography of essential papers (surveys, but also breakthrough papers) on matrix decompositions. What I have in mind prima... | g60432 | [
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<p>I have calculated the value of Pearson's <em>r</em> between two variables in SPSS, two tailed. Sample size is 81. The <em>r</em> value is -.21. The <em>p</em> value is .06. When I compute the 95% confidence intervals using bootstrapping with 2000 samples and the Bias corrected accelerated (BCa) option checked, I get... | g60433 | [
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<p>I've searched the web and these forums but couldn't find a subject that resembled my problem. If I missed something then I'd like to apologize upfront.</p>
<p>My problem is this. I have a given probability p, given by an outside agency and the number of successes n from an owned datasource. I'm interested in the po... | g16528 | [
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<p>I would like to compute the power of two distributions which are poisson with $n_1$ being large and $n_2$ being medium sized.
I have used the formula given by <a href="http://www.ucs.louisiana.edu/~kxk4695/JSPI-04.pdf" rel="nofollow">Krishnamoorthy and Thomson</a> for the C-test (see below).</p>
<p>$$\sum^\infty_{k... | g60434 | [
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<p>Can somebody help me with this approximation:</p>
<blockquote>
<p>as $m$ gets really large, $\dfrac{r}{m}$ gets really small and hence $\log\left(1+\dfrac{r}{m}\right) \sim \dfrac{r}{m}$.</p>
</blockquote>
<p>I don't understand how did $\log\left(1+\dfrac{r}{m}\right)$ approximately equals to $\dfrac{r}{m}$? Ple... | g60435 | [
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<p>I have a dataset where each row is an hourly measurement of certain fields (columns). For each column I then add another column that is its respective <em>z</em> score relative to the entire population.</p>
<p>If I then group by month by calculating the aggregate mean for all merging rows, are my <em>z</em> scores ... | g60436 | [
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<p>Can anyone recommend a library for time series data mining tasks other than predictive modeling and statistical analysis? There seem to be a number for these purposes (e.g., Gretl), but nothing for the tasks of:</p>
<ul>
<li>Classification</li>
<li>Clustering</li>
<li>Subsequence search</li>
<li>Anomaly detection</... | g60437 | [
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<p>ReLU has a range of [0, +Inf). So, when it comes an activation value z=0/1 produced by ReLU or softplus, the loss value computed by cross-entropy : loss = -(x*ln(z)+(1-x)*ln(1-z)) will turn to NaN.
As i know, my variables are run in theano.tensor type which cannot be modified after defined. So, I cannot simply chang... | g60438 | [
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<p>Suppose we have IID random variables $X_1,\dots,X_n$ with distribution $\mathrm{Ber}(\theta)$. We are going to observe a sample of the $X_i$'s in the following way: let $Y_1,\dots,Y_n$ be independent $\mathrm{Ber}(1/2)$ random variables, suppose that all the $X_i$'s and $Y_i$'s are independent, and define the sample... | g60439 | [
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<p>How could I compute the first order autocorrelation of the process $x_t = \delta + \phi x_{t-1} + \eta_t$? Could anyone give me some pointers?</p>
<p>I tried this:</p>
<p>$E(\delta + \phi x_{t-1} + \eta_t - \frac{\delta}{1- \phi})(\delta + \phi x_{t-2} + \eta_{t-1} - \frac{\delta}{1- \phi})$. But how could I compu... | g16532 | [
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<p>I am estimating a economic growth regressions using dynamic panel data.
My specification is as folllows:</p>
<p>$$\ln Y_{i,t} = a \ln Y_{i,t-1} + bX_{i,t} + e_{i,t}$$</p>
<ul>
<li>$Y$ measures income per capita</li>
<li>$X$ is the independent variable of interest, which represents a certain share of GDP (e.g. 0.05... | g60440 | [
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<p>This might be a better fit in the Mathematics or Philosophy StackExchanges, as I think I'm fundamentally facing a problem of logic, but I'll throw it out here first to avoid cross-posting. </p>
<p>I have two surveys - Survey A and Survey B. I want to validate Survey A's findings against Survey B's.</p>
<p>I have o... | g60441 | [
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<p>I am trying to figure out which cross validation method is best for my situation. </p>
<p>The following data are just an example for working through the issue (in R), but my real <code>X</code> data (<code>xmat</code>) are correlated with each other and correlated to different degrees with the <code>y</code> variab... | g60442 | [
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<p>I have always been confused about how to properly interpret PCA results. </p>
<p>My data looks like this and it's a big table with more than 5 million rows and 12 columns.(the first few lines are all 0...) Each column is for an individual which has more than 5 million observations (numbers).</p>
<pre><code>> he... | g60443 | [
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... |
<p>Does anyone know of a tool that I can use to generate a set of data with known correlations (and to put the icing on the cake - output this in json,csv,txt or some common format)?</p>
<p>I am working on some data visualizations and want to evaluate which ones can more easily allow a user to spot correlations - visu... | g60444 | [
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<p>I need some help about some data.</p>
<p>I have an indicator of performance and a likert scale. </p>
<p>Would it make sense if I assigned a value to each category on my likert scale (ex.: <code>really easy=5, easy=4, medium=3, hard=2, really hard=1</code>) and multiplied this value by the frequency of observation ... | g60445 | [
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<p>I have a continuous response $Y_{ij}$ after taking repeated measures in an individual $i$. Altogether I measure $Y_{ij}$ 5 times (j=1..5) under different types of subject motion: still1, still2, nod, shake and free.
I also measure how much each subject moved in each of these motion types and this variable ($m_{ij}... | g60446 | [
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<p>I need to implement the spatial vector autoregression model developed in <em>Beenstock, M. and D. Felsenstein. 2007. Spatial Vector Autoregressions. Spatial Economic Analysis 2 (2): 167-196</em>. </p>
<p>Is there a package in any software to estimate this model? If not, what the better way to go? I thank the attent... | g60447 | [
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<p>I have split my data set into four categories but one of them only has four data points in it. </p>
<p>I have run K-S normality tests on the other three categories which are each normal and when the data set is not split into four it is also normal.</p>
<p>For this fourth category, do I assume it is normal, and ru... | g60448 | [
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<p>Is there a more-or-less standard statistical test out there for checking whether a multivariate data set is being drawn from a multivariate Gaussian distribution?</p>
<p>I suppose I could calculate the empirical mean vector and covariance matrix and then use them to calculate the likelihood, but is there a better w... | g16543 | [
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<p>I'm doing an OLS regression of donations made by individuals to a not-for-profit organisation. The donation amount is the dependent variable and dummy (treatment) variables are the only independent variables.</p>
<p>The non-transformed treatment variable is significant (5% level), but when I take a log of the donat... | g60449 | [
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<p>I have a feature matrix n by p, where n is small.</p>
<p>I want to do <code>leave-one-out cross validation (LOOCV)</code>.Should I apply some dimension reduction technique (like PCA) for once at the very beginning, and perform LOOCV based on the new feature matrix, or apply PCA during each loop of LOOCV (so I get d... | g16544 | [
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<p>I'm really rusty at statistics and I'm trying to write some C# code where I feed in a list of numbers and it tells me whether or not the numbers are normally distributed. I generated 50 numbers from the following site with a mean of 0 and a variance of 1. </p>
<p><a href="http://www.random.org/gaussian-distribution... | g60450 | [
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<p>A nonnegative random variable $x$ has a continuous uniform distribution in the interval $(0,\theta)$. Therefore, the likelihood is given by:
$f(x|\theta) = \frac{1}{\theta}I(x\leq\theta)$, where $I$ is an indicator function. </p>
<p>But what is the Jeffreys prior for the parameter $\theta$? In particular, how to ha... | g16545 | [
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<h1>Question</h1>
<p>I would like to do a logistic regression where the independent variables are compared to the mean logit, rather than the logit being compared a certain reference group.</p>
<h1>Example</h1>
<p>The example below results in the logit of am==1 is being compared to carb==1 (the reference group):</p>... | g60451 | [
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... |
<p>I have a time series with observations that were collected quasi fortnightly over several years. However, there are between 23 and 26 observations per year. The time series is not equidistant, due to bad weather or holidays where no sampling occurred. Is it legitimate to average these observations to obtain a freque... | g41302 | [
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0.021510833874344826,
-0.0023422474041581154,
0.006711864378303289,
0... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://stats.stackexchange.com/questions/4220/probability-distribution-value-exceeding-1-is-ok">Probability distribution value exceeding 1 is OK?</a> </p>
</blockquote>
<p>I followed the <a href="https://www.coursera.org/course/ml" rel="nofollow"... | g49345 | [
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0.06821859627962112,
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0.03... |
<p>I would like to know if anyone knows how to apply the <code>arima</code> results to calculate missing values in the observation period. I am looking for something similar to <code>forecast.arima()</code>, that forecasts values based on <code>arima</code> results.</p>
<p>Does anyone has experiences in using data fr... | g16546 | [
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<p>I have three equations and don't understand why I missed points. All that was said was "simplify."</p>
<p>B^4Yt = c + et</p>
<p>(B-0.6B^3)Yt=(2+5B+0.8B^2)et</p>
<p>Yt=(1+B^3/B)et</p> | g60452 | [
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<p>I have a big dataset I want to find correlations in. So far I have been unsuccessful. I'm wondering whether it would be a good idea to either:</p>
<ol>
<li><p>Take the average of all neighboring entries in all my variables. (That means if I have a vector $X=(x_1,\ x_2,\ x_3,\ x_4,\ \ldots)$ I would transform that o... | g16554 | [
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<p>I am doing some classification task with Support Vector Machines (SVM).
I am using libSVM (with Matlab support) to predict probability estimates matrix. However, the libSVM displays message that;
Model does not support probabiliy estimates
Below is my sample code;
(train_label contains labels for training data and ... | g60453 | [
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<p>I am interested in finding expressions for the marginal distributions of the off-diagonal terms in a Wishart-distributed random variable.</p>
<p>More specifically, suppose $X$ is an $n \times p$ matrix, each row of which is independently drawn from a $p$-variate normal distribution with zero mean:
$X_{(i)}{=}(x_i^1... | g16555 | [
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<p>I was trying to understand better when we can learn a unique parameter for linear regression and how much data is required to get one. </p>
<p>Say that we want to learn a parameter $\theta$ such that empirical risk is minimized $R_n(\theta)$. For that we want:</p>
<p>\begin{align}
\bigtriangledown R_{n}( \theta )_... | g60454 | [
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<p>IN OLS linear models, fitted (predicted) and residuals scores are uncorrelated. I was under the impression that the same held true in mixed models. However, I have here an example model where fitted and (conditional) residual scores are correlated. Is there a theoretical justification for this to happen, or a good r... | g21911 | [
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<p>I am doing linear mixed models using lme4 and this is the results of model comparison:</p>
<pre><code>> anova(lmer5,lmer6,lmer32)
Df AIC BIC logLik Chisq Chi Df Pr(>Chisq)
lmer32 9 43172 43226 -21577
lmer6 21 43190 43315 -21574 6.3081 12 0.8998
lm... | g16556 | [
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0.02361331135034561,
0.0271273422986269,
-0.02760... |
<p>I'm trying to learn more about noise, power spectral density (PSD) and statistical variances. With regard this I'm trying to compute the power spectral density of white noise. However, when I do I get a very odd symmetry. My spectrum seems to be symmetric around the central frequency value, which is obviously incorr... | g16557 | [
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<p>This is a very basic question about cross-validation. Say that I have a sample size of 2901(or any difficult to divide number). How do I split this up into <strong>equal</strong> partitions (other than n=1)? And how big should I make each partition?</p>
<p>For example, if I make each partition size 300 (which gives... | g60455 | [
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0.016... |
<p>A survey found that 70% of college professors believe that their online education courses are as good as or superior to courses that use traditional face-to face instruction. </p>
<p>What is the null hypothesis? </p> | g60456 | [
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<p>Recall stochastic gradient descent (for regression):</p>
<p>$\theta = 0 $</p>
<p>$ \text{Randomly select } t \in [1,n]\{\\
\quad \theta^{(k+1)} = \theta^{k} + \eta_{k}(y^{(t)} - \theta \cdot x^{(t)})x^{(t)}\\
\}$</p>
<p>I was following some notes and it said that to have stochastic gradient descent converge i... | g60457 | [
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0.04... |
<p>I'm reading <a href="http://cseweb.ucsd.edu/~elkan/ECML2011LinkPrediction.pdf" rel="nofollow">this paper</a> about matrix factorization. In the paper they want to combine the features of the nodes in the model (page 6). First they illustrate the simple idea of combining the features of two nodes in a weighted linear... | g60458 | [
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0.02229829505085945,
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-0.03... |
<p>Let $X_1,X_2,...,X_n$ be a fixed number of Bernoulli random variables. My problem is to find a distribution for $Y$ such that for some function $f$, we have $Y=f(X_1,X_2,...,X_n)$. There are two candidate functions to use, $max$ or $avg$. I have no idea if an average function would work here or not but I think it'd ... | g60459 | [
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0.009662287309765816,
... |
<p>I want to estimate a multivariate variance function in R. That is, I want to allow the variance (as well as the mean) to vary according to some set of independent variables. </p>
<p>In this particular case, I want to estimate the effects of a set of typical demographic covariates (age, race, education) on the var... | g38032 | [
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<p>Is this formula right?</p>
<p>$$\renewcommand{\Pr}{\mathbb P}\Pr[\cap_{i=1}^n A_i] = \sum_{i=1}^d (-1)^{i-1} \sum_{|K|=k} \Pr[\cup_{k\in K} A_k],$$
with $K$ a subset (without repetition) of $\{1, ..., n\}$. </p>
<p>I have found a similar formula that expresses $\Pr[\cup_{i=1}^n A_i]$ in terms of $\Pr[\cap_{k\in K}... | g16562 | [
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0.0434645377099514,
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0.07087177783250809,
0.007395961321890354,
0.0226... |
<p>Does it matter if a dependent variable has a normal distribution or not when it is used in a regression?</p> | g49588 | [
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<p>I have a dataset where I am interested in calculating a slope for each observation / row. </p>
<p>I have dependent variable $Y$ that is continuous. Every $Y$ is unique to a zipcode.
and my independent / predictor variables are measured over time for every $Y$,
say $x_1$ to $x_{20}$. I am looking for a slope for e... | g60460 | [
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<p>I'm using different models to model count data, the purpose of modelling is prediction. Values vary from 0 to 7. I try to use cross-validation method to assess out-of-sample predictive perfomance, but what error measure should I use? Is RMSE enough? What other methods of models comparing and assessment can I use?</p... | g60461 | [
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<p>When doing natural language processing, one can take a corpus and evaluate the probability of the next word occurring in a sequence of n. n is usually chosen as 2 or 3 (bigrams and trigrams). </p>
<p>Is there a known point at which tracking the data for the nth chain becomes counterproductive, given the amount of... | g16567 | [
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<p>What is the best way to automatically select features for anomaly detection?</p>
<p>I normally treat Anomaly Detection as an algorithm where the features are selected by human experts: what matters is the output <em>range</em> (as in "abnormal input - abnormal output") so even with many features you <em>can</em> co... | g16568 | [
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<p>I'm new to concept of HMMs. I have trained 2 HMMs separately. </p>
<p>HMM1 is trained with symbols A, B, C. </p>
<p>HMM2 is trained with symbols D, E, F. </p>
<p>I have a set of observation symbols in the set V={A,B,C,D,E,F}.</p>
<p>In testing phase, I'm extracting a symbol by trying to associate a test vector t... | g46108 | [
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0.008385... |
<p>A common pre-processing step for ML algorithms is whitening of data.</p>
<p>It seems like it is always good to do whitening since it de-correlates the data, making it simpler to model.</p>
<p>When is whitening not recommended?</p>
<p>Note: I'm referring to de-correlation of the data.</p>
<p>Thanks.</p> | g46109 | [
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0.027184033766388893,
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0.0150173120200634,
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0.04323441... |
<p>Suppose to have a valid correlation function on $R^2$ that depends on the distance. For example if the distance between two point is $h$, the correlation function can be $\exp(-\phi h)$, where $\phi$ is a parameter.
Now if instead of $R^2$ we are on a cylinder: $R \times D$ where $D$ is a circle. My question is:
T... | g60462 | [
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<p>Conducted a survey (pre and post) on four questions using Likert scale. Based on the number of responses for agree and strongly agree pre and post intervention, computed the relative improvement. I want to know if this relative improvement is statistically significant or not. What test should I do? </p> | g60463 | [
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0.02835243195295334,
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0.0023... |
<p>I'm looking for a way to model and extract features from multivariate temporal data (e.g., multi-channel audio recordings).</p>
<p>I'm specifically interested in deep learning methods such as RBM, sparse autoencoders and so on.</p>
<p>Most methods I encountered consider only one dimension of the data, or maybe a 2... | g46111 | [
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0.01162038929760456,
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0... |
<p>What is the minimum number of data points required for a kernel density estimation to be considered non-misleading/acceptable/adequate?</p>
<p>Is there a some rule based on how dispersed the data is?</p>
<p>For example, if the inter-quartile range is "small enough", do you need less points than if the inter-quarti... | g16571 | [
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0.01817362941801548,
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... |
<p>I have a question about glm model fitting of my data. The distribution shape is likely to follow a poisson distribution, but the response variable is not count/rate, but continuous decimals with both positive an negative values （as shown below).</p>
<p><img src="http://i.stack.imgur.com/yt95b.jpg" alt="enter imag... | g3551 | [
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... |
<p>I ran a study looking at MEG (EEG with magnets) responses in the gamma-band (30-50Hz) range across multiple days. The following data is the timing of the initial response in that range (in seconds), in a n(subject)*m(raters(in the case different sessions)) matrix</p>
<pre><code>0.1025 0.068333333 0.088333333 0.15... | g60464 | [
-0.01884002797305584,
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-0.03379220515489578,
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0.05128428712487221,
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0.05920617654919624,
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0.004821224138140678,
0.008238040842115879,
0.030158743262290955,
-0.023784006014466286,
0.... |
<p>I have a dataset from a clinical trial for which all cancer patients received radiotherapy, but at different times following surgical removal of their tumour. So more simply, I have a variable, time to radiotherapy, and I want to investigate its relationship to survival.</p>
<p>What I think I need to do for the ana... | g60465 | [
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-0.0... |
<h1>Methods:</h1>
<p>From the <a href="http://aimotion.blogspot.com/2010/09/tools-for-machine-learning-performance.html" rel="nofollow">machine learning literature</a>, I understand different parameters can show performance of model in machine learning. I would briefly expand my understanding with confusion matrix:</p... | g16573 | [
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0.09704966843128204,
0.0060... |
<p>I'm working on a research project for which there is some proprietary information that I can't provide here. However, I will do my best to lay out as much information as I can.</p>
<p>In this project we performed a full factorial with two numeric independent variables: concentration (3-levels) and time (4-levels). ... | g60466 | [
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0.02... |
<p>I have an incomplete dataset and default setting in Eviews is listwise deletion. </p>
<p>Running my regression (regressing a continuous variable on 22 dummy variable regressors, unfortunately there is no data available to use a continuous variable as a regressor) with OLS and default setting yields exactly the same... | g60467 | [
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-0.028795290738344193,
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0.02385951578617096,
0.0072339437901973724,
... |
<p>I am trying to run a post-hoc power analysis on a previously published report. The intent is to calculate the average obtained power for (the equivalent of) Cohen's effects of d = .20, .50, .80) for all main effects and contrasts. </p>
<p>The study design is as follows: N = 240, repeated measures mixed (split-plot)... | g60468 | [
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<p>I have a small, unbalanced data set (70 positive, 30 negative), and I have been playing around with model selection for SVM parameters using BAC (balanced accuracy) and AUC (area under the curve). I used different class-weights for the C parameter in libSVM to offset the unbalanced data following the advice here (<a... | g60469 | [
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<p>I have a set of distributions (histograms) relating to data sampled from two different populations. Within each population I have $n=15$ distributions. I am looking for a statistical test that will tell me whether the two populations are statistically different, or not, based on the distributions within them.</p>
<... | g60470 | [
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0.010612430050969124,
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0.018193023279309273,
... |
<p>Does a checksum ensure absolute data integrity? That is, if a piece of data several gigabytes long changes a single bit, the odds are dependable that the checksum will be different, particularly with strong hash functions like SHA256?</p>
<p>Phrased differently, I'm asking whether a checksum offers assurance of rea... | g60471 | [
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<p>I have a dataset of educators and the courses that they designed. My original thought was to do a multilevel model where courses are nested within educators, and the outcome is whether the course ever was offered publicly to students. I was fitting this model using <code>melogit</code> in Stata.</p>
<p>However, I r... | g60472 | [
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<p>The <strong>Wilcoxon signed ranked test</strong> tells us if the median difference between paired data can be zero. The test is executed by computing a statistic, then a z-score and comparing it to a critical value. </p>
<p>The thing that I find shocking is that we </p>
<p><strong>discard all the pairs with same v... | g16578 | [
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<p>I'm a complete rookie when it comes to logistic regression and I seem not to be quite aware of the concept of deviance residuals. Could anyone help me interpret this plot? As far as I know these residual values should fall along the intercept.
<img src="http://i.stack.imgur.com/cicv5.png" alt="std_deviance_residuals... | g60473 | [
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0.04123800992965698,
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-0.... |
<p>I would like to basically ask what the title says. </p>
<p>What is the difference between <em>Primal</em>, <em>Dual</em> and <em>Kernel</em> Ridge Regression? People are using all three, and because of the different notation that everyone uses at different sources is difficult for me to follow. </p>
<p>So can some... | g22050 | [
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<p>I have been assigned a task where I need to solve a business case. Let me explain what information I am looking for:</p>
<p>I have historical data of several products and I need to forecast the time required for the sales for a given amount.</p>
<p>For example:</p>
<p>If the turnover is 5,000,000.00€ and the cost... | g60474 | [
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<p>I'm running a logistic regression with a small sample size: I corrected my data for outliers after checking the standard error (1.07) and the confidence intervall (0.51 - 11.55) for one of my variables. Those with a cook distance > 1 and DFBeta > 1 were excluded which resulted in an even higher standard error (2.15)... | g60475 | [
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0.01685236021876335,
-0.0159... |
<p>Suppose I am fitting a linear model, and I have two continuous predictors <code>x1</code> and <code>x2</code>. I think that they might interact, so I add the (linear) interaction term to my model (i.e., the pointwise product <code>x1 * x2</code>).</p>
<p>Now, as a rule of thumb, it seems to me that as soon as I do ... | g60476 | [
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<p>Assume I have a physical system in which I am sampling data from either a binomial distribution with a $p$ of 0.5, or from an alternation between a $p$ of 0.25 and 0.75. But the result is such that in this case it appears $p = 0.5$ as well.</p>
<p>So lets say for example I do a 1000 coinflips and get 500 heads. So ... | g49917 | [
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0.0015909632202237844,
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<p>I want to compare two linear models. <code>lm3</code> is the full model, <code>lm4</code> is the restricted model. </p>
<pre><code>lm3 <- lm(gamble ~ sex + status + income + verbal, data=teengamb)
lm4 <- lm(gamble ~ income, data=teengamb)
</code></pre>
<p><strong>First</strong>, I want to use an F-test to de... | g60477 | [
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<p>How do I interpret a negative confidence interval when comparing two population means?</p>
<p>For example, a confidence interval is $(-23.11, -1.02)$, what is the significance of these values being negative? Is it strictly signifying that $\bar{x}_1 < \bar{x}_2$ ?</p> | g16584 | [
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<p>In, for example, the <a href="http://www.mrc-bsu.cam.ac.uk/bugs/documentation/exampVol1/bugs.html" rel="nofollow">BUGS manual</a> or the upcoming book by Lee and Wagenmakers (<a href="https://webfiles.uci.edu/mdlee/BB_Free.pdf" rel="nofollow">pdf</a>) and in many other places a type of notation is used that to me se... | g16585 | [
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0.... |
<p>I have a dataset with columns that represent lagged values of predictors. To illustrate with a simple example, suppose we had car sales data for 3 years and the only predictors available were income and population for a number of car dealers, the dataset could be represented as follows,</p>
<pre><code>ID IncLag1 ... | g16587 | [
0.012642533518373966,
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-0.03172451630234718,
-0.04313508793711662,
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0.023752322420477867,
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0.04789400100708008,
0.039888493716716766,
0.08556967973709106,
-... |
<p>I tried to fit a curve to the black points using the following code. Why is the fit so bad? Do I need to fit another type of function?</p>
<pre><code>fit <- nls(grad ~ theta1/(1 + exp(-(theta2 + theta3*x1))),
start=list(theta1 = 4, theta2 = 0.09, theta3 = 0.31), trace=TRUE)
p = predict(fit)
plot(x1... | g60478 | [
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... |
<p>I'm actually not so sure if this is the right place to ask the question, but let's see if anyone could give some interesting ideas.</p>
<p>I would like to build a financial model which describes a business' Exit strategy. What I mean is that I would like to build a model that models various capital inputs, various ... | g16588 | [
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0... |
<p>I've been reading <a href="http://www-stat.stanford.edu/~tibs/ElemStatLearn/">Elements of Statistical Learning</a>, and I would like to know why the Lasso provides variable selection and ridge regression doesn't.</p>
<p>Both methods minimize the residual sum of squares and have a constraint on the possible values o... | g49719 | [
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<p>I have a data set with two variables, V1 and V2. V1 is a continuous variable, whereas V2 is a binary variable.</p>
<p>I would like to estimate the mean of V1. V2 is known to be adding error to V1 (V2 being there skews the data left, whereas it being absent skews the data right, both to the same degree). I would lik... | g60479 | [
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<p>Let's say I have a model:
$$Y_i = \beta_0 \beta_1^{X_i} \epsilon_i$$</p>
<p>(note: This is slightly different than the more common example case of $Y_i = \alpha e^{\beta x_i}\epsilon_i$.)</p>
<p>I can take the log of $Y$:
$$\log Y_i = \log\beta_0 + X_i\log\beta_1 + \log\epsilon_i$$</p>
<p>Assuming all the usual a... | g60480 | [
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-... |
<p>This is from the book <em>The statistical sleuth--A course in methods of Data analysis</em> Chapter 20, Exercise 12(c)-(e). I am using logistic regression to predict carrier with possible predictors <code>CK</code> and <code>H</code>. Here is my solution:</p>
<pre><code>Carrier <- c(0,0,0,0,0,1,1,1,1,1)
CK ... | g49391 | [
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-0.03796205669641495,
-0.06865096837282181,
0.033799707889556885,
0.0698196068406105,
0.0033... |
<p>I am currently with a medical imaging project. Just wondering how to measure the shape of a sphere. For example, how to give a measurement that an object is more like a sphere than the other?</p>
<p>I know some algorithm can give the 'roundness' in 2D, but a measure of 'sphereness' in 3D would be more helpful.</p>
... | g48725 | [
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0.0027437214739620686,
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0.017367474734783173,
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0... |
<p>A Regression with ARIMA errors is given by the following formula (saw on Hyndman et al, 1998):</p>
<p>$Y_t = b_0 + b_1 X_{1,t} + \dots + b_k X_{k,t} + N_t$</p>
<p>where $N_t$ is modeled as an ARIMA process.</p>
<p>If we have that the model for $N_t$ is ARIMA$(0,0,0)$, then $N_t = e_t$, and $Y_t$ is modeled by an ... | g60481 | [
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<p>I'm studying Biomedical Computer science and I have to research a paper about genotype-phenotype association.</p>
<p>In this paper the authors use a correlation analysis by first calculating the Pearson correlation and then calculating the hypergeometric distribution to filter out insignificant associations.</p>
<... | g46125 | [
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<p>I think people here could guide me in solving a problem related to anomaly detection in Computer Science. The term <em>anomaly</em> here refers to some undesired event occuring in the system like a virus infection.</p>
<p>I could get to know about it from more than one source. For example, after having extracted a ... | g16594 | [
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0.00830... |
<h3>Description</h3>
<p>I want to use Kolmogorov-Smirnov test to check how given clusters of 1D points differs from normal distribution (original question here: <a href="http://stats.stackexchange.com/questions/95493/how-to-test-which-data-match-model-at-best/95632?noredirect=1#95632">How to test which data match mode... | g60482 | [
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0.0... |
<p>I'm wondering how can I justify my sample size! I have 45 observations and 6 independent variables from which one is control variable. Is there any rule of thumb or specific test in this regard?</p>
<p>Many thanks,</p> | g60483 | [
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<p>I have a question regarding Multidimensional Scaling. I used the dataset <code>eurodist</code> from the package <code>datasets</code> to generate a 2 dimensional configuration of the distances between European cities. I expected a nearly exact representation of the location for the cities (although the points could ... | g60484 | [
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<p>I'm currently working on a project where my model is a GLM with a beta distribution. The dependent variable is bimodal. I've done this before, in Stata, but I'm having some difficulty interpreting what R has put out. I ran the model using the VGLM command from the VGAM package. For some reason, it has produced two c... | g60485 | [
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<p>Is there a package in R that can estimate panel data with cross-sectional <a href="https://en.wikipedia.org/wiki/Seemingly_unrelated_regressions" rel="nofollow">seemingly unrelated regression</a> generalized least squares weights (like in EViews)? </p> | g60486 | [
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... |
<p>I have some data that has runs of 0s with some 1s thrown in. For example: </p>
<pre><code>000000000100000000010000000000000000000111111100000000
</code></pre>
<p>However, the 1s are much more sparse. </p>
<p>I want to calculate a measure of how "runny" the data is. What I mean by this is I want to have a low va... | g21936 | [
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<p>I am starting out on my PhD journey, and the ultimate goal that I set before myself is developing ANNs that would monitor the environment they work in and dynamically adjust their architecture to the problem at hand. The obvious implication is temporality of data: if the data set is not continuous and doesn't change... | g45041 | [
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0.0363... |
<p>I am trying to create a bayesian model for the following problem: One has a barrel that contains many white balls and a few red balls. One has an uninformed prior on the concentration of red balls (distribtion A), and one takes repeated samples (e.g. of 20% of the balls). In addition - one removes a percentage (foll... | g60487 | [
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<p>I need to learn a Bayesian Network Structure from a dataset. I read the book titled "Learning Bayesian Networks" written Neapolitan and Richard but I have no clear idea.</p>
<p>According to the book from the data i can:</p>
<p>1) Create all the DAG Pattern, where a DAG Pattern is an equivalence class of DAG (in th... | g60488 | [
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<p>I have about 1000 subjects ($id$) and each of them has some baseline variables (demographic variables $X1, X2, X3, Xn$, which can be continuous, factors). Every subject is classified by two raters ($rater1$, $rater2$) in 2 factors. </p>
<ol>
<li>How can I evaluate and describe the concordance between the raters?</l... | g60489 | [
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-0... |
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