question stringlengths 37 38.8k | group_id int64 0 74.5k |
|---|---|
<p>While analysing the effect of environmental data on the activity of an animal species (the latter given as count data) I am fitting negative binomial GLMs with one predictor using the MASS library in R. Unfortunatley, the data set is very small (n=7 to 9).</p>
<p>In some cases, the theta value in glm.nb gets very l... | 36,713 |
<p>I have just started using the autoencoder package in R. <a href="http://cran.r-project.org/web/packages/autoencoder/index.html" rel="nofollow">http://cran.r-project.org/web/packages/autoencoder/index.html</a></p>
<p>Inputs to the autoencode() function include lambda, beta, rho and epsilon.</p>
<p>What are the boun... | 74,067 |
<p>The idea of degrees of freedom is pretty well sunk into my head, but I was wondering could someone perhaps give me few easy examples on how one would determine the number of degrees of freedom? </p>
<p>For example: Lets say that we have a sample of $n$ observations $x_1, x_2, ..., x_n$ following some distribution.<... | 49,341 |
<p>I apologise for the mix-up. Am trying to do a diallel analysis involving three parents in poultry. I tried using SAS05 program but it didnt work, i guess it was designed for diallel analysis involving 4-12 parents. I will appreciate any advice or direction on how to perform diallel analysis with 3 parents using eith... | 74,068 |
<p>My understanding of information entropy is that it requires the input probabilities to sum to 1.</p>
<p>So, for a sequence a,a,b,b you then have -([1/2 log2 1/2] + [1/2 log2 1/2]) = 1</p>
<p>Are there versions of information entropy that don't require probabilities to sum to 1? Or, is there a way to measure entrop... | 74,069 |
<p>In section 6.2, in the second paragraph of p. 335 (image below) of <a href="http://books.google.com/books?id=DG-6QgAACAAJ&dq=9780131464131&hl=en&sa=X&ei=bBfiT8WtJqbs2QXXv527Cw&ved=0CEIQ6AEwAA" rel="nofollow">"Probability and statistical inference 7e" by Hogg and Tanis</a> states: </p>
<blockquot... | 49,858 |
<p>I have been reading a lot about Dynamic Time Warping (DTW) lately. I am very surprised that there is no literature at all on the application of DTW to irregular time series, or at least I could not find it.</p>
<p>Could anybody give me a reference to something related to that issue, or maybe even an implementation ... | 36,721 |
<p>Several texts (both online and published books) have been reviewed prior to asking this.</p>
<p>What diagnostics are accepted as best practise for a generalised linear mixed-effects model fitted in R using glmmPQL. I am modelling mortality incidence (count data) using repeated measures, longitudinal survival data. ... | 36,722 |
<p>Hello: I am a computer science student working as a research assistant in an undergrad IR lab, feeling spectacularly out of my element.</p>
<p>Given an input of a single continuous value and a vector of several dozen boolean values, I must estimate the expected value of a single continuous value and output it. I ha... | 38,179 |
<p>I am doing a permutation to know if two datasets are significantly different. These datasets, both, have a median of 1 (in fast, 60% of observations in one datasets and 80% of the other dataset are the same observation).</p>
<p>Said that, my permutation test gives me a p-value of 1 (they are the same distribution).... | 29,195 |
<p>I am familiar with the debate surrounding Bates's decision to exclude p-values for mixed effects regression coefficients in lmer. However, I operate in a very p-value-focused discipline and am trying to clear something up. </p>
<p>What are the degrees of freedom for group-level predictors in a two-level model? I ca... | 44,232 |
<h3>Context</h3>
<p>I have two processes that each emit an event at various times:</p>
<pre><code>Times that event A occurs: 1, 15, 47, 73, 108
Times that event B occurs: 2, 18, 75, 90, 112, 140
</code></pre>
<p>I suspect that there is a weak causal relationship from A to B</p>
<ul>
<li>Process B is sometimes tri... | 74,070 |
<p>The standard error of an estimator is defined as the square root of the the estimator variance (or mean squared error, MSE, for unbiased estimators). More specifically, if we wanted to get the standard error of the sample mean $\bar{X}$, we would divide the variance of the sample used to calculate $\bar{X}$ by the s... | 74,071 |
<p>On page 10 of <a href="http://www.chicagobooth.edu/jar/conference/docs/DoMarketsUnder-Kumar.pdf" rel="nofollow">this paper</a> the author states that </p>
<blockquote>
<p>In this section, I use monthly Fama and MacBeth (1973) logit
regression [...]</p>
</blockquote>
<p>to examine the type of forecast. My quest... | 74,072 |
<p>I just went through the following work <a href="http://epublications.bond.edu.au/cgi/viewcontent.cgi?article=1199&context=ijbf" rel="nofollow">http://epublications.bond.edu.au/cgi/viewcontent.cgi?article=1199&context=ijbf</a> and was wondering what is the difference between model (9) on page 12 which models ... | 74,073 |
<p>In an experiment several measurements are taken using similar but different measuring instruments. (The number of measurement tools used in a single experiment could range from 2 to 500 instruments, but most have a low number (~2 - 3) of instruments used.) Since all the instruments are measuring the same effect, it ... | 74,074 |
<p>What are the main ideas, that is, concepts related to <a href="http://en.wikipedia.org/wiki/Bayes%27_theorem">Bayes' theorem</a>?
I am not asking for any derivations of complex mathematical notation.</p> | 36,728 |
<p>I am looking for a list of modeling algorithms (as a package in <code>R</code>) that can accept: </p>
<ol>
<li>Continuous or categorical predictors </li>
<li>Continuous response </li>
<li>Can effectively treat missing values. For example, <code>glm</code> and <code>randomForest</code> discard records with missing v... | 74,075 |
<p>I have a set of samples, for which I know the "true groups". For this samples I have about 200 binary variables, I would like to know a method to select the subset of variables, that gives me a clustering as closer as possible of my known groups.</p>
<pre><code># sample labels
labelColors2 <-c("black", "black","... | 36,729 |
<p>The EM algorithm roughly has two steps.<br>
E-Step:<br>
Calculate the conditional expectation of the likelihood function given the data $x_1, . . . , x_n $ and the current estimates of parameters $\Theta^{[k]}$. So the objective function would be
$Q(\Theta, \Theta^{[k]})=E[\ln(\Theta,x_1, . . . , x_n)|x_1, . . . , x... | 19,095 |
<p>Let $D$ be a data set containing $n$ instances of two variables $x_1$ and $x_2$. Further let $x_1$, $x_2$ be independent according to some measure like linear correlation or mutual information etc.</p>
<p>How do we find a reordering of the values of $x_2$ that results in some predetermined (achievable) correlation ... | 49,925 |
<p>I draw following figure using the <code>DLNM</code> package in <strong>R</strong>.</p>
<p>Datasheet a has variables <code>y</code> and <code>x1</code>. I assume that the continuous dependent variable <code>y</code> has gaussian distribution and that continuous independent variable <code>x1</code> has a relationship... | 74,076 |
<p>I have a sample of about 1000 values. These data are obtained from the product of two independent random variables $\xi \ast \psi $. The first random variable has a uniform distribution $\xi \sim U(0,1)$. The distribution of the second random variable is not known. How can I estimate the distribution of the second... | 74,077 |
<p>I am trying to learn the difference between the three approaches and their applications.</p>
<p>a) As I understand,</p>
<pre><code>AIC = -LL+K
BIC = -LL+(K*logN)/2
</code></pre>
<p>Unless I am missing something, shouldn't the K that minimizes the AIC minimize BIC as well since N is constant. </p>
<p>I looked a... | 74,078 |
<p>I have a dataset:</p>
<pre><code>y = array([ 4460000., 2100000., 938000., 500000., 204000., 130000.,
124000., 118000., 106000., 100000., 98000., 98000.,
97000., 99000.])
x = array([ 470., 955., 1700., 2900., 5520., 7000., 8500.,
9700., 14600., 22000., 27000.... | 74,079 |
<p>If one-third of the persons donating blood at a clinic have a O+ blood, find the probability that the 5th O+ donor is the fourth donor of the day.</p> | 74,080 |
<p>I am trying to fit the different variables types and measurement levels into some logic, like a tree diagram, and I am not sure about some things. On one hand, you have <strong>quantitative</strong> variable vs. <strong>qualitative</strong>. For a quantitative, you have <strong>continuous</strong> or <strong>discret... | 36,732 |
<p>I am trying to make two plots next to one another using the R cookbook <code>multiplot</code> function, although I am getting the following error:</p>
<blockquote>
<p><code>Aesthetics must either be length one, or the same length as the dataProblems:v.x</code></p>
</blockquote>
<p>Can someone help? My code is be... | 74,081 |
<p><strong>The scenario:</strong></p>
<p>Consider that I have some 100 GB of raw data. When I extract features from it using the traditional, well-known approaches in my area, I get (say) <strong>100,00,000 instances</strong>. When I build supervised machine-learning models (using Decision tress and Bayesian Networks ... | 74,082 |
<p>How to Predict the Dependent variable in lmer? Do we have any Package or function already buit in R?</p> | 74,083 |
<p>The likelihood could be defined by several ways, for instance :</p>
<ul>
<li><p>the function $L$ from $\Theta\times{\cal X}$ which maps $(\theta,x)$ to $L(\theta \mid x)$</p></li>
<li><p>the random function $L(\cdot \mid X)$</p></li>
<li><p>we could also consider that the likelihood is only the "observed" likelihoo... | 36,735 |
<p>Does the pdf of an mvn variable even exist when there is high correlation?</p>
<p>I want to use an algorithm (actually it is the cross-entropy method for estimating a rare-event probability) that needs the pdf value of the mvn distribution, that is mvnpdf(x,mu,Sigma). </p>
<p>However, my Sigma is close to singular... | 74,084 |
<p>I get from a specific experiment 3 outputs. Each is the information of some physical quantity in the direction x,y or z. The way we extract the information from those signals is by fitting.</p>
<p>In the data extracted from fitting, some parameters depend only on the direction of the physical quantity we want to me... | 36,736 |
<p>Hello and thanks for looking at my questions.</p>
<p>I'm sure this is a very simple question but I just cant seem to understand it</p>
<p>A committee of three is selected from a pool of five individuals : two females (A and B) and three males (C,D,E)</p>
<p>If the committee is selected at random, what is the prob... | 74,085 |
<p>I would like to use R to solve a problem I have. I don't even know what to call a problem of this kind and I'm finding Googling difficult. My guess is that this kind of problem already has R packages to help solve it, but I'd very much appreciate help defining the problem.</p>
<p>I want to select the optimum comb... | 33,408 |
<p>This time, I have a more theoretical than computational predicament. I have a path model that I am interested in testing on a data set with two groups. It is a very simple two predictor model outlined below, and I am using the ML-SEM function on Mplus v.7 to analyze the data.</p>
<pre><code> y = x1 + x2
</code></pr... | 74,086 |
<p>I have set of time series for various days (same frequency and source). I need to choose a subset of it, and they together will forecast future values.</p>
<p>Currently I am simply using X out of Y time series with lowest AICc values when fitted into an ARIMA model.</p>
<p>I want to know which tests I could use to... | 19,099 |
<p>I understand that at least one system for automatically modeling 3D objects from image data exists. Autodesk appears to have developed a good method. Does anyone know the basic structure and algorithms commonly used in such a system? </p>
<p>My technique would include the use of a multilevel neural network (NN). T... | 74,087 |
<p>I'm looking for an R package (or a combination of packages) that would allow me to perform MCMC estimation of a GMM model, with a user-specified moments function.</p>
<p>I've looked at the CRAN Bayesian task-view, but I can't seem to find what I'm looking for, packages being either too general (eg. mcmc) or too spe... | 74,088 |
<p>Is the probability calculated by a logistic regression model (the one that is logit transformed) the fit of cumulative distribution function of successes of original data (ordered by the X variable)?</p>
<p><strong>EDIT:</strong> In other words - how to plot the probability distribution of the original data that yo... | 36,745 |
<p>I am working on my thesis. My main regression model is the following:</p>
<ol>
<li><p>$Y=x_1*{\rm Payment}+x_2*{\rm Country}+x_3*{\rm Industry}...$</p>
<p>All independent variables are dummy / binary variables. In a next step I divide my sample and construct the following two regression:</p></li>
<li><p>$Y=x_2*{\r... | 74,089 |
<p>I want to simulate or calculate probabilities of combinations of group membership for different sample sizes (e.g., n= 3, 4, 5, 10, or 100) for two groups (of the same sample size). Each outcome could be male/female and young/old. The population is 50% male and 50% young.</p>
<p>What is the probability of getting: ... | 74,090 |
<p>I'm trying to add a softmax layer to a neural network trained with backpropagation, so I'm trying to compute its gradient.</p>
<p>The softmax output is $h_j = \frac{e^{z_j}}{\sum{e^{z_i}}}$ where $j$ is the output neuron number.</p>
<p>If I derive it then I get</p>
<p>$\frac{\partial{h_j}}{\partial{z_j}}=h_j(1-h_... | 74,091 |
<p>I have 8, 1-minute audio excerpts, all that feature the same music. Four of them were recorded by a middle school music ensemble (2 expressive, 2 unexpressive) and four by a high school music ensemble (2 expressive, 2 unexpressive). </p>
<p>I am getting participants in the MS ensemble, the HS ensemble, and a set ... | 74,092 |
<p>We have a daily report that takes the days p90 website latency data and compares it with the same day over the past four weeks and tells whether the p90 latency has gone up or down for a particular day. </p>
<p>I was also planning to build a weekly report that takes the average p90 latency delta for current and pre... | 74,093 |
<p>calculating recall/precision from k-fold cross validation (or leave-one-out) can be performed either by averaging the recall/precision values obtained from different k folds or by combining the predictions and then calculate one value for each of the recall and precision. </p>
<p>My data is composed of 1000 samples... | 74,094 |
<p><em><strong>Can anyone provide a brief overview of the most popular training algorithms for perceptrons?</em></strong></p>
<p>I am currently training my perceptron using standard stochastic gradient descent (online gradient descent) with a fixed learning rate.</p>
<p>There seems to be hundreds of different algorit... | 74,095 |
<p>After reviewing related questions on Cross Validated and countless articles and discussions regarding the inappropriate use of <a href="http://en.wikipedia.org/wiki/Stepwise_regression" rel="nofollow">stepwise regression</a> for variable selection, I am still unable to find the answers that I am looking for in regar... | 74,096 |
<p>Apologies for the uninformative title. This is actually a fairly simple problem which I could easily do myself in matlab or perhaps stata, but the professor demands it be in SAS, which seems to have been designed for robots not humans.</p>
<p>Say I have a matrix of farm output data with rows of crops at the farm a... | 74,097 |
<p>My table of chi-square test for homogeneity has 3x5 cells, 3 samples to a likert scale item. Most cells in the table have a frequency count of less than two, so it is recommended to discard the column of which contains a cell with frequency of less than two. How will this affect my hypothesis if I discard the entire... | 31,251 |
<p>Is the likelihood ratio test ($-2 \log L$) basically like the partial F-test in that you are using it for logistic regression instead of linear regression?</p> | 703 |
<p>This question is an extended version of <a href="http://stats.stackexchange.com/questions/18294/what-does-equal-a-priori-class-probabilities-mean">this one</a>.</p>
<p>As you can see here, two distributions are equal, I need to compute the parameters a,b,c,d and e. Could you show me a way to do that?</p>
<hr>
<p>... | 74,098 |
<p>There are two main probabilistic approaches to novelty detection: parametric and non-parametric. The non-parametric approach assumes that the distribution or density function is derived from the training data, like kernel density estimation (e.g., Parzen window), while parametric approach assumes that the data comes... | 74,099 |
<p>Here is the head of my data set (<code>tjornres</code>): </p>
<pre><code> Fish.1 Fish.2 MORPHO DIET
1 1 2 0.03768 0.1559250
2 1 3 0.05609 0.7897060
3 1 4 0.03934 0.4638010
4 1 5 0.03363 0.1200480 ... | 36,758 |
<p>It seems the Bonferroni method (dividing experimentwise alpha by # of comparisons) for choosing the p level to fix the experimentwise alpha (when doing many pairwise comparisons) is more conservative than just solving $1 - (1 - p)^k = .05$ to get the alpha to use for each of the $k$ pairwise comparisons. Why not ju... | 44,480 |
<p>Came across an interesting problem today. You are given a coin and x money, you double money if you get heads and lose half if tails on any toss.</p>
<ol>
<li>What is the expected value of your money in n tries</li>
<li>What is the probability of getting more than expected value in (1)</li>
</ol>
<p>This is how I ... | 74,100 |
<p>I've performed a three-way repeated measures ANOVA; what post-hoc analyses are valid? </p>
<p>This is a fully balanced design (2x2x2) with one of the factors having a within-subjects repeated measure. I'm aware of multivariate approaches to repeated measures ANOVA in R, but my first instinct is to proceed with a si... | 36,759 |
<p>I am trying to use the dirmult package in R to find the parameters of the dirichlet multinomial distribution. However When I run the code, I see that it appears to be minimizing the Likelihood rather than maximizing. Here is a sample trace:</p>
<pre><code>> foo <- dirmult(data)
Iteration 1: Log-likelihood val... | 74,101 |
<p>From Cassela and Berger's Statistical Inference,</p>
<blockquote>
<p>Theorem 7.5.1 (Lehmann-Scheff) Unbiased estimators based on complete
sufficient statistics are unique.</p>
</blockquote>
<p>I wonder if the condition is not necessarily strong? I.e. is it true that </p>
<blockquote>
<p>unbiased estimators ... | 74,102 |
<p>When carrying out OLS multiple linear regression, rather than plot the residuals against fitted values, I plot the (internal) Studentized residuals against fitted values (ditto for covariates). These residuals are defined as:</p>
<p>\begin{equation}
e^*_i = \frac{e_i}{\sqrt{s^2 (1-h_{ii})}}
\end{equation}</p>
<p>... | 48,444 |
<p>I have a small dataset of count data that has a number of zero measurements. My overdispersion is fairly large. Due to this, I was drawn to using the glmmadmb package.</p>
<p>I understand how to compare the fit of the distributions (poisson, nbinom etc) using AICtab.</p>
<p>What I am struggling with is how to asse... | 74,103 |
<p>I have a set of <strong>Observation Symbol Sequences</strong> which I have to <strong>test</strong> against a set of Trained HMM classifiers. I seem to understand the <a href="http://en.wikipedia.org/wiki/Log_probability" rel="nofollow">advantages</a> of using Log Probability over regular probabilities.</p>
<p>In t... | 35,490 |
<p>Good morning</p>
<p>I searched regarding change in variance over time, but everything I saw was about relatively long time series. I have a series of 5 time points, equally spaced, but with different people missing at each time point. There are about 15 variables I am interested in, all medical things like levels... | 74,104 |
<p>I have data for an application's installs per day and their ranking in the store for the following day. Each user/installation can be further broken down into two categories - those that installed it because of an ad, and those that installed it on their own (e.g., by word of mouth).</p>
<p>From this data, I want t... | 48,447 |
<p>I'm trying to use a multiple regression (in Excel) to determine the effectiveness of foreign aid on GDP growth. I've forgotten everything since college...</p>
<p>My plan is to run a regression using established determinants as a 'baseline'. Then run another adding in my independent variable of 'aid expenditures',... | 74,105 |
<p>I can understand what a handwritten digit is, but what is meant by "binary image"? Can someone explain it?</p>
<p>I am studying machine learning concepts. In doing so, I've come across many types of inputs. For example: binary, continuous, and discrete. The inputs are provided through MNIST handwritten image datase... | 29,168 |
<p>I'm trying to improve accuracy in a Naive Bayes classifier that uses a bunch of features. I have a hunch that removing some features may actually improve performance. My reasoning is for a particular feature the estimated PDFs across the classes may be different slightly because of the limited amount of learning d... | 74,106 |
<p>I have a data set which looks something like this (not real data):</p>
<pre><code>conc Resp
0 5
0.1 18
0.2 20
0.3 23
0.4 24
0.5 24.5
0 5
0.1 17
.. ..
</code></pre>
<p>which happens to fit perfectly to the Michaelis-Menten equation:</p>
<blockquote>
<p>Resp = max_value * conc ... | 74,107 |
<p>Suppose using an specific sampling method I have generated a sample but I now want the normalising factor to be able to calculate the probabilities. Can I consider the sum of the values as their normalising factor. Could you please also give a source for that?</p> | 74,108 |
<p>The question emerged while reading Ch. 3 of <a href="http://www.gaussianprocess.org/gpml/" rel="nofollow">Rasmussen & Williams</a> . In the end of this chapter, the authors gave results for the problem of handwritten digits classification (16x16 greyscale pictures); features are 256 pixel intensities + bias. I w... | 74,109 |
<p>I am new to R and would like your help with lme formula for partially crossed random effect in a random-intercept, random-slope model. In the longitudinal data I have, each subject (barring some dropouts) was tested at 5 different occasions. The standardized tests were administered by 3 different examiners, with 2 o... | 74,110 |
<p>I am new to machine learning and can't get my head around this problem. I have two patient datasets, the first ($D_1$) contains $Y,Z,X$ that convey blood-sample information and the second ($D_2$) contains $W,T,X$ that convey x-ray information. In both datasets, $X$ is the common diagnostic output. </p>
<p>Since th... | 74,111 |
<p>I'm trying to figure out the practical meaning of less degrees of freedom regarding the results of t-test results. For example: If I have two dependent samples and would like to compare their means using a t-test. If I use both tests for dependent and independent samples I will have more degrees of freedom in the de... | 74,112 |
<p>I have a dataset of fraudulent orders from some business. Each order has a bunch of features such as order_amount, address, state, city, phone_number, and name. Obviously a criminal would not be using his/her real name when making a fraudulent order. So I was wondering if there was any sort of machine learning st... | 74,113 |
<p>I have a set of 1000 datapoints of measured concentrations that may include up to 300 values which are censored (below the detection limit that the lab could reliably measure). The range of detection limit values vary, such as <2, <3, <7 etc. My data is neither normal or log-normal, and I've used non-para... | 33,569 |
<p>I am doing a leave-one-subject-out for a mixed-effects model for a longitudinal data analysis, in which the model is fitted to all subjects minus one at a time, and the left-out subject becomes validation data. </p>
<p>The original model is formulated as:</p>
<pre><code>model<-lme(score~time*covariate,random=~... | 74,114 |
<p>I have built and refined a regression model using the <code>ordinal</code> package in <code>R</code>. The measure is $0>1>2>3>4>5$ (Yes/No questions) and is repeated every 10 minutes for an hour (episode) within the same person, twice a week for up to 6 weeks, but average 3 weeks. I have 6000 such obs... | 74,115 |
<p>The univariate exponential Hawkes process is a self-exciting point process with an event arrival rate of:</p>
<p>$ \lambda(t) = \mu + \sum\limits_{t_i<t}{\alpha e^{-\beta(t-t_i)}}$</p>
<p>where $ t_1,..t_n $ are the event arrival times.</p>
<p>The log likelihood function is</p>
<p>$ - t_n \mu + \frac{\alph... | 36,777 |
<p>(To see why I wrote this, check the comments below my answer to <a href="http://stats.stackexchange.com/questions/24588/quantiles-vs-highests-posterior-density-intervals">this question</a>.)</p>
<h2>Type III errors and statistical decision theory</h2>
<p>Giving the right answer to the wrong question is sometimes c... | 74,116 |
<p>In "R - project" I am trying to estimate the panel data <code>lm</code> model with <code>plm</code> function. When I include 3 dummy variables into the regression it doesn't appear in the summary of the model, but when I estimate a simple <code>lm</code> model it appears.</p>
<p>Why is it so? What should I do to es... | 36,779 |
<p>here is my situation. I am weighting a packet of material that has 10 individual units in it. In the end of the day I would like to know the average weight and variance of the individual units but the problem is that I cannot weight each unit individually since I would have to destroy the packet to get to the indivi... | 74,117 |
<p>It seems to me that normalized ERR (<a href="http://don-metzler.net/papers/metzler-cikm09.pdf" rel="nofollow">Expected Reciprocal Ranking</a>) scores (ERR scores of your ranking algorithm divided by ERR score calculated for the ground truth ranking) are more useful than the unscaled ERR scores, but I have not seen n... | 74,118 |
<p>The scenario is like this:</p>
<p>I have a cohort with 2000 people, half of them taking DRUG, the other half not taking it. I would like to check interactions between DRUG and the other variables in the model:</p>
<ul>
<li><p><strong>Method 1:</strong></p>
<p>Firstly I got a original model: <code>y1=a1*AGE+b1*BMI... | 74,119 |
<p>The convergence theorem for Gibbs sampling states:</p>
<p>Given a random Vektor $X$ with $X_1,X_2,...X_K$ and the knowlegde about the conditional distribution of $X_k$ we can find the actual distribution using Gibbs Sampling infinitly often.</p>
<p>The exact theorem as stated by book (Neural Networks and Learning ... | 36,782 |
<p>I put this question because while reading the benefits of standardizing explanatory variables or not, I read <em>good but contrasting</em> opinions about standardizing when there are interaction in the model. </p>
<p>Some talk about how problems of collinearity are removed when standardizing (e.g. <a href="http://... | 49,325 |
<p>I am trying to do a box-cox transformation with swift. I have a dependent variable, annual foreign sales of companies (in US\$ thousands) which contains zeros, for a set of panel data. I have been advised to add a small amount, for example, 0.00001 to the annual foreign sales figures so that I can take the log, but ... | 74,120 |
<p>What is the expected length of a streak of heads or tails when flipping a coin? What distribution is this?</p>
<p>I'm pretty sure the answer is 2. But I don't know what distributions it is..</p>
<p>I did the following R code:</p>
<pre><code>l=10000
longest.stk = avg.stk = numeric(l)
for(i in 1:l){
x=sample(0:1, 1... | 74,121 |
<p>I have two spectra of the same astronomical object. The essential question is this: How can I calculate the relative shift between these spectra and get <strong>an accurate error estimate</strong> on that shift?</p>
<p>Some more details if you are still with me. Each spectrum will be an array with an x value (wavel... | 74,122 |
<p>Random variables are usually denoted with upper-case letters. For example, there could be a random variable $X$. Now, because vectors are usually denoted with a bold lower-case letter (e.g. $\mathbf{z} = (z_0, \dots, z_{n})^{\mathsf{T}}$ and matrices with a bold upper-case letter (e.g. $\mathbf{Y}$), how should I de... | 74,123 |
<p>I am trying to run a discrete duration model for analyzing (monthly) unemployment using survey data. I have household-level data, and as such I would like to control for the household effects in my model. I thought to do this by either allowing for cluster effects in the estimation of the standard errors or by rando... | 74,124 |
<p>Suppose I have <code>N</code> correlation coefficient matrices, containing the Pearson correlation coefficients of <code>k</code> different time series of some quantity measured for every subject of an experiment.</p>
<p>The correlation matrices are then rescaled from the <code>[-1,1]</code> interval to <code>[0,1]... | 36,790 |
<p>Basically I'm trying to fit garch(1,1) model with arima order from auto.arima</p>
<pre><code>> assign(paste("spec.ret.fin.",colnames(base.name[1]),sep=""),
+ ugarchspec(variance.model = list(model = "fGARCH", garchOrder = c(1, 1),
+ submodel = "GARCH", external.regressors = NULL, variance.targeting = FALSE)... | 36,791 |
<p>Over at <a href="http://skeptics.stackexchange.com/a/11164/23">Skeptics.StackExchange</a>, an answer cites a study into electro-magnetic hypersensitivity:</p>
<ul>
<li>McCarty, Carrubba, Chesson, Frilot, Gonzalez-Toledo & Marino, <a href="http://www.national-toxic-encephalopathy-foundation.org/lsustudy.pdf" rel... | 36,794 |
<p>What does "return rate" (<code>tasa de retorno</code> in spanish) mean in population ecology models? In context of capture-mark-recapture models. I have found many articles on this, but no definition!</p>
<p>I've also found the term "recapture rate". What is it? Is it the same as "return rate"?</p> | 40,307 |
<p>In fitting a two-component Student's t mixture distribution to some data (standardized GARCH residuals) one of the components has an estimated degree of freedom of 0.6.
This means that even the first moment of the mixture distribution would not exist.</p>
<p>The gamlss.mx package in R is used for estimation. gamls... | 74,125 |
<p>I am working on a model and I have calculated the EVPI, EVPPI and the EVSI.</p>
<p>I need to interpret the graph of the Expected Value of Sample Information (EVSI), what should I say? The graph consists of the sample sizes as the x-axis and the EVSI as the y-axis.</p>
<p>I know that the EVSI calculation is part of... | 35,424 |
<p>I fit the logistic regression model for gender and drink for the data ihd using the following command </p>
<pre><code>model<-glm(ihd~as.factor(gender)*as.factor(drink),Family='binomial',data=ihd)
</code></pre>
<p>My question is how can I get the estimated log odd-ratio for: </p>
<ol>
<li>gender in non-drinker... | 74,126 |
<p>I want to apply LDA in my study. I want to use LDA to classify my data. My data is a $M\times 20$ matrix, it means there are $20$ features in my data. How can I apply LDA for my data?</p>
<p>And another question: Does LDA only work on data which have only two features ($M\times 2$ matrix)?</p> | 74,127 |
<p>I am attempting to recreate the model in this paper:</p>
<p><a href="http://abdulpinjari.weebly.com/uploads/9/6/7/8/9678119/pinjari_etal_transportation_iatbr2009specialissue.pdf" rel="nofollow">Pinjari (2011)</a></p>
<p>in which the author uses a 4 equation system with discrete choice dependent variables in each o... | 74,128 |
<p>I know that one can easily get variance (unconditional) of a Garch (r,s) process
:
$\sigma^2= \frac { \alpha_0 } { (1- \Sigma_{i=1}^r \alpha_i - \Sigma_{j=1}^s \beta_j ) }$</p>
<p>However I am struggling to get an analytical expression for Unconditional variance when there is an ARMA part also in Garch..</p>
<p>t... | 74,129 |
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