question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I like to be able to use dynamic linear modelling (DLM) on a time series data to perform forecast. I am currently using lm function but I like explore dlm to see the difference. My data looks like this:</p>
<pre><code> structure(list(DATE = structure(c(1389287553, 1389287583, 1389287613,
1389287643, 1389287673,... | g61805 | [
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<p>I started to use the function <code>multinom</code> of <code>R</code> package <code>nnet</code> in order to fit several conditional probability distributions with the multinomial logistic model. I need the parameters of the fittings in order to pass them to a Java program, which will compute the probabilities and us... | g31863 | [
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<p>I have following data:</p>
<p>ultra-sound audio recording, and I have the raw data of those samples, and of course the Fourier Transform data for those samples. Each dataset is assigned a value (for example 7.2 units), and I need some sort of algorithm which chooses which frequencies to use to get to that value.</p... | g61806 | [
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<p>Is there any way to specify manually, the validation/test and training set in nntool in matlab.</p>
<p>Actually, I wanted to test the performance of nn with increasing number of hidden neurons. So what I do is call this function </p>
<pre><code>net = newfit(train_data', targets', n);
</code></pre>
<p>everytime wi... | g18553 | [
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<p>My study is assessing whether there is a correlation between two medical conditions (endometriosis) and bleeding disorders.</p>
<p>The case participants have endometriosis and the controls do not.</p>
<p>In both case and control we are measuring a number of different haemostatic variables (clotting factor levels, ... | g61807 | [
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<p>I have the following time series current measurement recordings at 5,000 samples per seconds for 10 minutes:</p>
<p><a href="https://docs.google.com/file/d/0ByIzsQrgb6ILakdaVVJkcEFUUGc/edit?usp=sharing" rel="nofollow">https://docs.google.com/file/d/0ByIzsQrgb6ILakdaVVJkcEFUUGc/edit?usp=sharing</a></p>
<p>I am tryi... | g61808 | [
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<p>This sounds easy, but I don't know of a good statistical method for it.</p>
<p>I have a time series that has (good) data points that range from ~3.5 to 30. The data are collected by an automated sensor. However, there are flawed measurements in the time series-- the sensor will sometimes read values that are typica... | g61809 | [
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<p>When is it appropriate to use linear regression for a binary outcome?</p>
<p>I understand that it is conventional to use logistic regression for a binary outcome because it generates a linear list of outcomes which avoids the problem of generating estimates greater than 1 or 0. However my professor advised me to us... | g49624 | [
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<p>If I have two independent variables and they are dummy variable along with other independent variables and I run a linear probability model, I want to compare whether the coefficients of two dummy variables are statistically different from each other. I do not know how to compare that. Could someone help me on that?... | g61810 | [
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<p>I am looking at standardized regression weights (i.e., Beta weights). I was thinking of reporting the errors next to the weights in a figure, but upon some thought I was debating whether such errors even exist. I know un-standardized regression weights have standard error parameters, but do standardized regression w... | g61811 | [
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<p>Let $X$ be a sample from the distribution which is the mixture of the useful signal with the distribution $\xi(\theta)$ and a uniform noise $U[a, b]$. The probability of observing $U[a, b]$, the parmeters $a$ and $b$ are not known. </p>
<p>I would like to estimate $\theta$. How do I do it?</p>
<p>By the mixture I ... | g18560 | [
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<p>I sample two timecourses:</p>
<ul>
<li>$X=shardNoise+noise_X$</li>
<li>$Y=signal+\beta*sharedNoise+noise_Y$</li>
</ul>
<p>($signal$, $sharedNoise$, $noise_X$ and $noise_Y$ are independent from each other)</p>
<p>My goal is to 'regress-out' $sharedNoise$ from $y$, so my estimation of $signal$ won't be affected by ... | g18561 | [
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<p>I got this sentence in one of paper, but I dont understand what does it mean??</p>
<p>"Training a learningbased classifier such as an SVM on an imbalanced dataset often requires parameter fine-tuning, making the system less generic "</p> | g18562 | [
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<p>i have the following problem that makes me crazy.
COnsider a trivariate normal variable, let $\sigma_1^2$, $\sigma_2^2$ and $\sigma_3^2$ be the variance of the three components and $\rho_{1,2}$, $\rho_{1,3}$ and $\rho_{2,3}$ be the correlation coefficients between the components. I want to obtain the covariance matr... | g61812 | [
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<p>My (not too deep) understanding of the curse of dimensionality that affects a classification algorithm, such as k-Nearest Neighbor, is that at higher dimensions the 'sparsity' of euclidean space kicks in (this can be seen, for example by comparing the volume/content/measure of the unit ball with respect to the unit ... | g61813 | [
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<p>I understand how to compute Distance Transform for <a href="http://www.mathworks.com/help/images/ref/bwdist.html" rel="nofollow">BW image</a>
In BW image we can calculate the distance of the pixel with non zero pixel value using Eucledian Distance.</p>
<p>But I dont undertand how to calculate it for <a href="http:/... | g18565 | [
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<p>What do you think about result from my arima model? Should I need to change the model. I do not want to change it because it is the best I have but p values do not seem fine</p>
<p><img src="http://i.stack.imgur.com/VqrhR.png" alt="tsdiag"></p> | g61814 | [
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<p>I'm trying to understand what is happening in my Poisson regression. I have the following variables: Dependent variable: transactions(number of transactions(continuous)). Independent variables: education(years of education (continuous)),sex(binary),health(health status), income(continuous) other than salary, loan(bi... | g61815 | [
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<p>I've hit an interesting general problem and cannot work it out. I would be grateful for any pointers:</p>
<p>The problem: 5 players are randomly assigned a number x=1-5. A player compares his number with another random player. The player with the lower score leaves and the player with the higher score goes into t... | g61816 | [
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<p>I used Latent Semantic Analysis (LSA) to extract latent topics (i.e., the polynomials coefficient1*word1 + coefficient2*word2 + ...) from a certain corpus. I know that the larger the (absolute value of the) coefficient, the more important the word for that topic. But is there a better metric? Python's gensim package... | g61817 | [
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<p>What is autocorrelation and how it can effect the results of multiple regression in <em><strong>SPSS</strong></em>. Durbin-Watson value of <strong>1.04</strong> is acceptable or not? If this value effects the results, then how to <strong>correct</strong> it in SPSS. </p> | g18571 | [
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<p>I have two variable in my research. the first is managers commitment & the second is personnel satisfaction. so we have two population & two questionnaire, one for managers & the other with "different" questions for personnel. moreover the number of managers is different from the number of personnel. how... | g61818 | [
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<p>I came across variance stabilizing transformation while reading <a href="http://www.kaggle.com/c/asap-aes/details/evaluation">Kaggle Essay Eval method</a>. They use a variance stabilization transformation to transform kappa values before taking their mean and then transform them back. Even after reading the wiki on ... | g61819 | [
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<p>This is a very basic question on using R for classification. I'm trying to use rpart for classification task and would like to have a class label as a result, i.e. I use type="class" in predict method</p>
<pre><code>predict(tree, data, type = "class")
</code></pre>
<p>The class labels are "0" and "1". When I try t... | g18572 | [
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<p>I am using binary logistic regression; the dependent variable is 1 or 0; the independent variables are two groups: the first group includes continuous variables (<code>LNTA: logarthim of total assets</code>, <code>ROA: return on assets</code>, and <code>Leverage</code>; the second group includes categorical variable... | g61820 | [
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<p>When using canonical correlation analysis (CCA), we can integrate the dataset and label information via transforming the class label matrix <em>Y</em> into the class indicator matrix <em>T</em>. Such as: $T = (YY^T)^½Y$ in <a href="http://www.ncbi.nlm.nih.gov/pubmed/20733223" rel="nofollow">this article on LS CCA</a... | g18573 | [
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<p>I am currently planning on calculating the autocorrelation for various lags given a time series. However, my elements of the time series are "discrete" and abstract classes; i.e., no integers.</p>
<p>For example, my series could look like:</p>
<p>class A, class B, class A, class A ...</p>
<p>Of course I could now... | g61821 | [
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<p>I have seen something like </p>
<p>$4.1^{+2.1}_{-1.5}$</p>
<p>or </p>
<p>$4.1 [+2.1, -1.5]$</p>
<p>but I would like to know, what is the preferred way or something like a standard in scientific work (especially in physics/engineering)?</p> | g48518 | [
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<p>I used Tobit regression and wanted to test if the coefficients are significant. The problem is that when I run the R code I get t-values instead of z-values. I found code on how to calculate p-values for z-values and I'm wondering if you can use the same code for the t-values that you use for the z-values to calcula... | g61822 | [
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<p>A correlation coefficient is computed as $$r=Cov(X,Y)/(\sqrt{Var( X)}*\sqrt{Var (Y)})$$
What is the correlation coefficient of a number with itself then.
I have a noise function,assuming with a known value and variance; and I perform a correlation of noise with itself what should I get as the correlation coefficient... | g61823 | [
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<p>I need a package for missing data imputation in R. But since I am dealing with big data, the number of missing data entries can also be high. The packages which impute using mean or median are of course working fast, but more complicated packages which impute using regression or PCA take too long for a high number o... | g61824 | [
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-0.030363019555807114,
0.04213087260723114,
0.006883684545755386,
0.027673708274960518,
0... |
<p>Suppose that $X_1, X_2, \ldots, X_n$ (with $n > 0$) is a random sample from a non-central exponential distribution with probability density function:</p>
<p>$$f(x | \lambda, k) = \lambda * e^{-\lambda*(x-k)}$$ </p>
<p>Both the scale parameter ($\lambda$) and the <strong><em>shift parameter</em></strong> ($k$) ... | g18575 | [
-0.016568729653954506,
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-0.0... |
<p>Suppose that
$$ Y = b + aX + e$$
where you know that $E[Y|X] = b + aX$. Is it true that the model cannot suffer from omitted variable bias? If this is true, then it follows that omitted variable bias can always be considered as a funcional form bias (namely, changing the functional form $f(X)$ will remove the bias... | g61825 | [
0.05336590111255646,
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0.021... |
<p>What I'm trying to do is estimate the following GARCH(1,1) model in <code>R</code> with the <a href="http://hosho.ees.hokudai.ac.jp/~kubo/Rdoc/library/fGarch/html/garchFit.html" rel="nofollow">garchFit</a> function from the <code>fGarch</code> package:</p>
<hr>
<p>Mean equation:</p>
<p>$Y_t = a + bX_t + e_t$</p>
... | g33828 | [
0.01183832623064518,
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0.031741347163915634,
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0.05276269093155861,
0.027153903618454933,
-0.... |
<p>As part of my self study for Financial Economics, I came across simplifying the following expression,</p>
<p>$$\sigma Z_{0.25} + (2\sigma)(Z_{0.5} - Z_{0.25})$$</p>
<p>where $Z$ are independent <a href="https://en.wikipedia.org/wiki/Wiener_process" rel="nofollow">Brownian motion</a> ($Z_0 = 0$ and $Z_t-Z_s \mathtt... | g61826 | [
0.02933354489505291,
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0.0... |
<p>Suppose I have two power generating technologies, Coal and Oil, of which the generating cost components(total generating cost = Capital cost+Fuel cost+Variable O&M cost+Fixed O&M cost) are correlated in the following manner:</p>
<pre><code> Oil
F... | g33837 | [
0.07353901118040085,
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... |
<p>One of the most serious shortcomings of covariance/correlation are the assumptions of linearity and normality.</p>
<p>What is the most natural generalization of these measures of dependence when you want to model the dependence structure of extreme events using heavy-tailed distributions, e.g. the <a href="http://e... | g61827 | [
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0.0001496251643402502,
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<p>Using Amelia in R, I obtained multiple imputed datasets. After that, I performed a repeated measures test in SPSS. Now, I want to pool test results. I know that I can use Rubin's rules (implemented through any multiple imputation package in R) to pool means and standard errors, but how do I pool p-values? Is it poss... | g61828 | [
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<p>I have an experiment where I am interested in comparing proportions. Basically, participants write 4 different essays to 4 different open ended questions. Each answer is rated on a categorical variable of 1, 2, and 3. However, it is possible to write an essay containing more than 1 category. I don't need to predict,... | g61829 | [
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0.04619847983121872,
... |
<p>The null and alternate hypotheses are:</p>
<p>$H0 : μ_d ≤ 0$<br>
$H1 : μ_d > 0$</p>
<p>The following sample information shows the number of defective units produced on the day shift and the afternoon shift for a sample of four days last month.</p>
<pre><code> Day 1 2 3 4
Day shift... | g61830 | [
0.04544655606150627,
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0.015872744843363762,
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0.04037093371152878,
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0.014232391491532326,
0.048920027911663055,
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0.0... |
<p>I would like to forecast the non-stationary time series, involving several crucial a-priori assumptions following from studying of instances of such series.</p>
<ol>
<li><p>I've constructed time-averaged one-point probability distribution function approximated by normal distribution. $$\hat p(x) = \frac{1}{\sqrt{2\... | g61831 | [
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0... |
<p>I’m reading R. Kreps' paper <a href="http://www.casact.org/pubs/proceed/proceed97/97553.pdf" rel="nofollow"><em>Parameter uncertainty in (log)normal distributions</em></a> and trying to figure out how the simulations were done. In order to generate Figure 1, Eqn (2.41) was used. So this is what I did in R:</p>
<p>T... | g61832 | [
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0.0013057503383606672,
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<p>Let say I have a 'kidney catheter' data set. Data are about the recurrence times to infection, at the point of insertion of the catheter, for kidney patients using portable dialysis equipment. Catheters may be removed for reasons other than infection, in which case the observation is censored. Each patient has exact... | g37999 | [
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<p>I am confused and just need some confirmation about calculating the relative variable importance value for the co-variates I used in AIC model selection procedures. I know that there is this one <a href="http://stats.stackexchange.com/questions/25322/relative-variable-importance-values-vs-magnitude-of-effect">discu... | g18585 | [
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0.09636788070201874,
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0.036216... |
<p>If I have a regression problem where I try to estimate the value of $y$ as function of $x_1 \dots x_d$:
$$
y = f(x_1,\dots,x_d)
$$</p>
<p>using a Boosted Regression Tree or a Random Forest Regression, is it possible to estimate the probability distribution of the output value (instead of only an estimate of $y$) :<... | g61833 | [
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0.025946933776140213,
0.07606112211942673... |
<p>Say we use a ruler to make a measurement of the width of a block of wood. We get some value like <code>4.2 +/- 0.1 cm</code>, where the error is our estimated error of our ruler's precision. Now we have four new individuals measure the same block of wood, and two of them obtain <code>4.5 +/- 0.1cm</code> and two obt... | g48532 | [
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0.01627887226641178,
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0.03399065509438515,
... |
<p>Estimating confidence intervals for non-normally distributed residuals can be accomplished using bootstrapping procedures, sandwich estimators or quantile regression.</p>
<p>But is there a way to calculate $\beta$ confidence intervals given the estimated value? That is, for each $\hat{Y}$ we know the residuals vari... | g18587 | [
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... |
<p>I have used a Likert scale in my survey, where respondents answer statements in terms of 1=strongly agree to 5=strongly disagree.
There are 5 items measuring a single type of 'need gratification' and there are 5 different needs. </p>
<p>After summing the five items for each need gratification, a score is obtaine... | g61834 | [
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... |
<p>I wanted to check what is the relative error of an estimated N(0, 1) density function. By relative error I mean:</p>
<p>$$\alpha(x) = E \bigg ( \frac{f(x|\hat{\mu}, \hat{\sigma})}{f(x|0,1)} \bigg ) - 1$$</p>
<p>where $f(\cdot, \mu, \sigma)$ is the normal pdf.</p>
<p>To get an estimate of $\alpha(x)$ I simulated $... | g61835 | [
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0.03... |
<p>I have a dataset that looks like this. </p>
<pre><code>test.takers item1 item2 item3 item4 item5 item6 item7 item8 item9 item10 item11 item12 item13 item14 item16 item17 item18 total_score
tt1 1 1 0 1 0 1 1 1 0 NA 1 1 NA 1 1 1 1 ... | g61836 | [
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0.004704711493104696,
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0.032904013991355896,
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... |
<p>I am trying to perform stepwise regression for variable selection in R.
In matlab, the <code>stepwisefit function</code> is able to work in <code>n < p</code> problems. Trying to use <code>step()</code> for such problems i get the error message <code>AIC is -infinity for this model, so 'step' cannot proceed</cod... | g49790 | [
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0.000029971412004670128,
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... |
<p>If I have 50 items and I want to compare the top 30. I have several cases to do the ranking , so which one is correct?</p>
<p>For simplicity I will replace in the example below 50 items with 5 ( A,B,C,D,E) , and top 30 = 3. So the cases: </p>
<p>1- Rank the 5 items using 2 different functions independently and the... | g61837 | [
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0.0... |
<p>I am trying to develop an intuition for why L1 regression is more expensive than L2 regression. Can somebody point me to some material that explains why this is the case</p> | g44966 | [
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<p>Most examples about <code>lmer</code> formula description in R target rather simple study designs. However, sometimes one is confronted with more complex designs and there is no documentation about a general rule to formula-construction. For instance, how would I formulate the following design:</p>
<ul>
<li>15 subj... | g28291 | [
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<p>Consider a random variable $X$ which has quartic exponential distribution: $$X \sim P(x)=\frac{1}{Z}e^{ax + bx^2 + cx^3 + dx^4}$$ How can one compute $Z$ or non-central moments $E X^k$ given that they exist? As far as I understand, there are no closed-form formulas for these quantities, but is there a good numerical... | g12463 | [
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<p>I am relatively new to statistics and not formally trained but have been given a complex problem to solve and need some guidance. I realise that I am out of my depth a bit here but would appreciate whatever help I can get bearing in mind that there is no budget for this and as a result it is not possible to purchase... | g61838 | [
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<p>Is there a way to train a neural network in the following manner:</p>
<p>You have $n$ observations in the training set.</p>
<p>The neural net will start with random weights, and produce $n$ outputs. I want to then apply a function, $f$, on these $n$ outputs. $f$ will output a single real valued number $\alpha$. Th... | g61839 | [
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<p>I'm doing some practice problems on methods of moments from a textbook. I am stuck on the following question:</p>
<p>The pdf of a one-parameter Weibull distribution is given by: </p>
<p>$f(x) = \begin{cases} 2\alpha xe^{-\alpha x^2}, &\mbox{if }\: x > 0 \\
0 & \mbox{otherwise}. \end{cases} $</p>
<p>Usi... | g61840 | [
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0.06104813143610954,
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0.06... |
<p>I would greatly appreciate some advise on a statistical problem that haunts me. </p>
<p>Suppose you wish to estimate the effect of $x$ on $y$, but the probability to observe $\{y_i, x_i\}$ also depends on the effect of $x$. Say, if $x_i > z_i$, then you don't observe $\{y_i, x_i\}$. If $x_i < z_i$, then you d... | g61841 | [
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0.... |
<p>Maybe a bit of a philosophical question - but can you ever truly have known parameters in data? I have a set of data for which the dataset is complete, but the parameters will still be estimates i believe?</p> | g361 | [
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... |
<p>This is not exactly a technical question related to any method, but this seemed like the best forum to ask this. The question I am asking is more along the lines of experimental data management. </p>
<p>I often run into situations where I have to compare several sets of similar results VISUALLY, for example experim... | g18593 | [
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0.06160043552517891,
0.0... |
<p>If anyone is interested, this question is prompted by the recent NBA Lottery results. In the past 20 years, the team with the worst record in the NBA has won the lottery exactly 3 times. The team with the worst record every year has a 25% chance of winning the number one overall pick. </p>
<p>Of course, many people... | g61842 | [
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<pre><code>str(test)
'data.frame': 767 obs. of 2 variables:
$ datefield: Ord.factor w/ 59 levels "1984-04-01"<"1984-07-01"<..: 1 2 3 4 5 6 7 8 9 10
$ somevar : num 43.7 55.6 43.5 54.1 42.8 ...
> str(Italy)
'data.frame': 1008 obs. of 2 variables:
$ year: Ord.factor w/ 48 level... | g61843 | [
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-0.03526991605758667,
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-0.... |
<p>I'm trying to estimate a binary function of $Y$~$Bernouli(p_{i})$ where $p_{i}=f(age)$ where f is an unknown continuous function. There are obviously a lot of methods to try to reconstruct f (splines, Gaussian processes, etc), but what if my age observations are collapsed into buckets (18-29, 30-44,etc)?</p>
<p>Obv... | g3854 | [
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<p>Previosuly I have asked how to compute some conditional probabilities, but I am missing this particular case:</p>
<p>lets say we now have 3 variables:
$T$, $L$, $E$:</p>
<pre><code> T L
\ /
E
</code></pre>
<p>So
$E$ depends on $T$ and $E$ depends on $L$</p>
<p>I have these probabilities:</p>
<p>... | g18597 | [
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<p>I plan to conduct a research study about Interaction Designers. </p>
<p>Prior to starting on sampling methods I am finding it very hard to get my hands on some demographics and statistics, e.g. How many people are registered to be employed as Interaction Designers, User Experience Designers etc. in a particular ter... | g38016 | [
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<p>Latent semantic indexing seems to work well; e.g. it is independent of language, etc.
However, it appears to use the similarity of frequencies of terms in the corpus to categorize them.</p>
<p>If this understanding is correct, is there a way to measure the size of the dataset that will give optimal performance?</p... | g61844 | [
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<p><a href="http://stats.stackexchange.com/q/1521/2192">Data Mining and Statistical Analysis</a> has a general discussion on stats vs data mining. If I may, narrow down the question a bit - are there any general demarcations that allows you to decide which approach is more suited for using - LDA or ARM? (other than app... | g61845 | [
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<p>When I insert the p-value <code>3.2531E-129</code> into excel's <code>CHIINV</code> function I get <code>#NOMBRE</code> as a result.<br>
How do I find or report the chi-square value if this doesn't work?<br>
Someone suggested I wrote out the 0 when the value was <code>6.1203E-05</code> to <code>0,0000061203</code>.<... | g33984 | [
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0.015429088845849037,
0... |
<p>Suppose $X_1,\ldots,X_n$ is a random sample from $N(\theta,1)$ so that $\theta\geq a$ .</p>
<p>How can I calculate minimax estimator $\theta$ under loss function $L(\delta,\theta)=(\delta-\theta)^2$</p> | g18599 | [
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<p>I am doing a study to analyze the effects of knocking out a particular gene on a certain behaviour in flies. After a log transformation, my observations have a normal distribution so I'm going to do a three-way ANOVA, with age as the first, sex as the second and genotype (mutant vs wild-type) as the third variable, ... | g61846 | [
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<p>Table 18.1 in the <a href="http://www-stat.stanford.edu/~tibs/ElemStatLearn/" rel="nofollow">Elements of Statistical Learning</a> summarizes the performance of several classifiers on a 14 class data set. I am comparing a new algorithm with the lasso and elastic net for such multiclass classification problems. </p>
... | g61847 | [
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<p>I'm dealing with a random sample and I have a question about its poststratification weights. Let's assume that: </p>
<ul>
<li>this is a random sample of addresses, but post-stratification weights have been calculated (using Census estimates) because the sample doesn't match the target population with respect to ... | g18606 | [
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<p>I have a largish data set (400,000 variables of 1000 samples). I would like to identify what is the best set of these variables for capturing most of the variance between samples. </p>
<p>What's the best way to perform an iterative principal component analysis that will perhaps go through X rounds of between Y and ... | g18607 | [
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<ol>
<li><p>What kinds of distribution have variance as a function of expectation, i.e. let $X$ be a random variable of a distribution, $Var(X) = f(E(X))$ for some function $f$ ? Sufficient conditions including typical examples of distribution (such as <a href="http://en.wikipedia.org/wiki/Exponential_family" rel="nof... | g18608 | [
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... |
<p>23 patients suffering from bruxism (grinding of teeth) have been given a treatment. Their baseline bruxism has been measured for three nights, then they were treated for 23 nights, then again the "post" baseline was measured for three nights.</p>
<p>The raw data looks like this:</p>
<pre><code>patient night scor... | g18610 | [
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0.018256235867738724,
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<p>I am trying to estimate a system of non-linear equations using 'systemfit' package in R. I have had issues with it. </p>
<p>The two equations share the same parameters i.e. "sigma", "al" and "ae". I expect them to take the same values across the two equations. By theory, I expect 'sigma's to be the same. Though, I ... | g61848 | [
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<p>I have a question concerning the significance of the seasonal dummies in my ARIMA-model (I do not use seasonal differencing or seasonal AR/MA as I have quite regular seasonality and I get better performance results): </p>
<p>What to do, if say 1 or 2 are significant but the rest are not? This happens to me particul... | g61849 | [
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<p>I am trying to put together a data-mining package for StackExchange sites and in particular, I am stuck in trying to determine the "most interesting" questions. I would like to use the question score, but remove the bias due to the number of views, but I don't know how to approach this rigorously.</p>
<p>In the ide... | g18615 | [
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<p>I have some data that a downstream system needs an optimized function of boolean logic for. Essentially I have data similar to:</p>
<pre><code>User cat1 cat2 cat3 cat4
1 0 0 0 1
2 1 0 0 1
3 0 1 1 0
</code></pre>
<p>I must optimize cat4 as a function like this: <code>(ca... | g18617 | [
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0.0092... |
<p>Currently we have a linear model which includes 3 independent variables and the dependent variable "Y" which is the predicted values (range from -0.5 to 2000) from the model. Now we want to leverage the same model by just removing one of the predictor (lets call that as X1). </p>
<p>One of my colleague suggested to... | g61850 | [
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<p>I'm working on a research project where we are trying to assess model fit improvement of our LDA model (the basic Blie et al., 2003 LDA approach). I'm looking for code that allows us to assess the perplexity of our LDA model as we tune it. </p>
<p>I know the R Package "topicmodls" has a perplexity function but my P... | g576 | [
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<p>I have a study where the goal is to see if a new diagnostic tool provides any addition to the old procedure. A set of patients have been diagnosed and classified into 7 categories, each corresponding to a given treatment. The new diagnostic tool is then used, and the patients are diagnosed and classified again. Pati... | g577 | [
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<p>The R plotting package ggplot2 has an awesome function called <a href="http://docs.ggplot2.org/0.9.2.1/stat_smooth.html">stat_smooth</a> for plotting a regression line (or curve) with the associated confidence band.</p>
<p>However I am having a hard time figuring out exactly how this confidence band is generated, f... | g18619 | [
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<p>First, I should state that I have searched on this site for the answer. I either didn't find a question that answered my question or my knowledge level is so low I didn't realize I already read the answer. </p>
<p>I am studying for the AP Statistics Exam. I have to learn linear regression and one of the topics is... | g61851 | [
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<p>I am producing a script for creating bootstrap samples from the <code>cats</code> dataset (from the <code>-MASS-</code> package). </p>
<p>Following the Davidson and Hinkley textbook [1] I ran a simple linear regression and adopted a fundamental non-parametric procedure for bootstrapping from iid observations, namel... | g35903 | [
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<p>In a multi-level model, what are the practical and interpretation-related implications of estimating versus not-estimating random effect correlation parameters? The practical reason for asking this is that in the lmer framework in R, there is no implemented method for estimating p-values via MCMC techniques when es... | g61852 | [
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... |
<p>F test and t test are performed in regression models.</p>
<p>In linear model output in R, we get fitted values and expected values of response variable. Suppose I have height as explanatory variable and body weight as response variable for 100 data points. </p>
<p>Each variable (explanatory or independent variable... | g61853 | [
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0.0038477524649351835,
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0.037826... |
<p>Am I wrong, or the standard way of optimizing a machine learning model is by evaluating the algorithm over the (initial) dataset for all possible combinations of parameters, and then pick up the one that gives the 'best' evaluation score? If we still don't get an acceptable score, we should then slice and dice the (... | g61854 | [
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0.011876460164785385,
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<p>There are 4 groups, each one having two 2 variables, X and Y. I am trying to understand the regression between them. For X variable I have 2 categories, positive and negative. I am not understanding how to compare the slopes and intercepts between X (positive and negative) and Y. Do I have to invert the negative val... | g18624 | [
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0.007490161340683699,
0.0330069437623024,
-0.015525752678513527,
0.030... |
<p>In <a href="http://ronan.collobert.com/pub/matos/2008_nlp_icml.pdf" rel="nofollow">Unified Architecture for NLP</a> paper time-delayed neural network proposed as a way to deal with variable length input. Input window slides over sequence and label each output with "time", then next layer takes max over time. But no ... | g61855 | [
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-0.03800313547253609,
0.022212503477931023,
0.03577830269932747,
0.046... |
<p>In GAM-based logistic regression pseudo-absence data is necessary to fit the model with corresponent presence data. In many cases, pseudo-absence data are generated 10 times more than presence records in order to ensure sufficient landscape variety in the pseudo-absences. To ensure that the presences and pseudo-abse... | g61856 | [
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0.050815649330616,
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0.016968395560979843,
-0.03360655903816223,
-0.01126317959278822,
0.06448890268802643,
0.0225... |
<p>Under what situations would MLE (Maximum Likelihood Estimates) equal LSE (Least Squares Estimates)?</p>
<p>I got an impression that under norm 2 ($L_{2}$), MLE and LSE are equal.</p>
<p>For example, the process of solving $\mathrm{min}||y−Ax||_{2}$ is actually the MLE estimation of parameter $A$ for random variabl... | g61857 | [
0.0184496883302927,
-0.07296515256166458,
0.01627182774245739,
0.035022299736738205,
-0.0285754706710577,
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0.005224915686994791,
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-0.0018496094271540642,
-0.02407131716609001,
0.002782142721116543,
0.04722398519515991,
0.03278... |
<p>Today I noticed <a href="http://stats.stackexchange.com/questions/63364/power-analysis-with-r">this question</a>, and I thought it would be helpful if we had a thread that listed resources that people could conveniently access for power analysis / sample size calculations, perhaps analogous to this thread: <a href="... | g61858 | [
0.02637658640742302,
0.008315927349030972,
0.0034527848474681377,
-0.01962948776781559,
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0.0024540522135794163,
0.025468556210398674,
-0.015385620296001434,
0.02021012455224991,
0... |
<p>I was wondering if it is necessary to mean center and set std to 1 to the both my xs and ys in linear regression or doing that to just xs is fine enough.</p>
<p>Lets say I use a different model, say neural networks, is it necessary to standardize. I want to know if it is good to standardize both xs and ys, whatever... | g49625 | [
0.013246418908238411,
-0.027755551040172577,
0.007410941179841757,
-0.04716314747929573,
0.029940446838736534,
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0.07664468884468079,
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-0.006221784744411707,
0.019470199942588806,
0.06712111830711365,
0.043712057173252106,
-0... |
<p>I have three time series of economic data based on quarterly observations; A, B and C, and I would like to ascertain the correlation (or not) between A and C as well as the correlation between B and S. The 1st order differenced time series of B passes the ADF and KPSS tests for stationarity. Series A & C fail th... | g61859 | [
0.037202972918748856,
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0.010529480874538422,
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0.05773905664682388,
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-0.012677574530243874,
0.07768115401268005,
0.01927971839904785,
0.0029902735259383917,
-0.0083... |
<p>Suppose we have the following classical normal linear regression model:</p>
<p>$$y_i = \beta_1 x_{1i} + \beta_2x_{2i} + \beta_3x_{3i} + e_i$$</p>
<p>where $e_{i} \sim iid.N(0, \sigma^2)$ for all $i = 1, 2, \cdots, n$ and $x_{1i} = 1$ for all $i = 1, 2, \cdots, n$.</p>
<p>Assume that we have known data values for ... | g61860 | [
-0.0029605883173644543,
-0.05805225297808647,
0.009278877638280392,
-0.09320233017206192,
0.02597018890082836,
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0.017021216452121735,
0.004288984462618828,
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-0.021340232342481613,
0.007936717011034489,
0.08135858923196793,
0.022958951070904732,
-... |
<p>I learned a linear regression model with some input xs and output ys. My ys are always positive. However, now when I test the model on my test data, I get negative values for ys. I know I can either take the absolute value of ys or make them 0. But that's not the right way to do it. What is the correct approach to d... | g61861 | [
0.009081453084945679,
-0.08117752522230148,
-0.005430308170616627,
-0.020241234451532364,
0.014545407146215439,
0.019470082595944405,
0.0006096471333876252,
0.00582411652430892,
-0.02681344375014305,
-0.021881630644202232,
0.02800774574279785,
0.03883125260472298,
0.07603172957897186,
0.01... |
<p>I am trying to put the two time series of my Excel spreadsheet (see link below), into a contingency table.</p>
<p><a href="https://www.dropbox.com/s/2f96oylxj97fuih/example.xls" rel="nofollow">https://www.dropbox.com/s/2f96oylxj97fuih/example.xls</a></p>
<p>The first series is the number of subscriptions per hour ... | g61862 | [
-0.007688624318689108,
0.059022314846515656,
0.0019753475207835436,
-0.06700079888105392,
-0.029831334948539734,
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-0.009080838412046432,
-0.03078204207122326,
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0.008453465066850185,
0.028581876307725906,
0.0185418501496315,
0.0038093707989901304,
... |
<p>I am trying to use Random Forest Regression in scikits-learn. The problem is I am getting a really high test error:</p>
<p><code>train MSE, 4.64, test MSE: 252.25.</code></p>
<p>This is how my data looks: (blue:real data, green:predicted):</p>
<p><img src="http://i.stack.imgur.com/qmhbs.png" alt="Forest regressio... | g38190 | [
-0.027537943795323372,
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0.003192356089130044,
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-0.04385896399617195,
0.02234838157892227,
-0.04421062394976616,
0.03346443548798561,
0.01404... |
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