All Questions

21 views

GRM or mixed effect models

I need your help. In experiment I have measured the grow of one plant on 40 locations. At one location different number of plants were measured, but always the same species. The distribution of ...
25 views

Fitting GARCH Model

I'am getting more and more familiar with this kind of model (and others models too). I'm now used to fit this model with my data (rmgarch package in R). How is it done ? What is the theory behind ...
16 views

I have numerous road segments that belong to a city. Each road segment as a weight that is given to it due to its level of 'connectivity' (‘impact’from a small side street to a motorway). So, small ...
36 views

prequential evaluation - classification

I perform prequential evaluation like this: start with a training set, classify a number of examples, then add the correctly classified examples in the training set and continue to classifying the ...
27 views

Test on the properties of two betas?

I have a set of observation. When I do an OLS I get a beta. After I remove some values I also get a beta. Now I want to test if the properties of two betas are the same? Pls give me a hint how to do ...
30 views

Methods for imputation of missing values with spatially autocorrelated data

I am looking at the spatial patterns of turnover in aquatic assemblages using gradient forest and generalized dissimilarity models in R. I have species and environmental data for more than 400 sites ...
27 views

Quadratic weighted kappa versus linear weighted kappa

When should I use quadratic weighted kappa or linear weighted kappa? I have two observers evaluating the classes of a number of objects. The classes are fail, pass1, pass2, and excellent (ordinal ...
33 views

Clustering mixed variables in SAS

I have following variables in my dataset: Working hours (numerical:ordinal) Effectiveness (categorical:ordinal ; 4 values-> (poor,average,good,best)) Satisfaction (categorical:ordinal ; 4 values-> ...
42 views

Linear relationship between explanatory variables in mutliple regression

I was reading the multiple regression chapter of Data Analysis and Graphics Using R: An Example-Based Approach and was a bit confused to find out that it recommends checking for linear relationships ...
117 views

Regression for a model of form $y=ax^k$?

I have a dataset which is statistics from a web discussion forum. I'm looking at the distribution of the number of replies a topic is expected to have. In particular, I've created a dataset which has ...
79 views

Linear regression explanations

In explaining simple linear regression, isn't it a bit misleading for many examples to illustrate a straight line going through some scatterplot? This seems to suggest that linear regression only ...
26 views

Is there any R package that can produce cube plots for 2 factors (in fact it is a square plot)? I want something similar to the first plot at the end of this page on factorial plots. In the package ...
57 views

Dummy variables in multiple regression, why use an intercept?

When performing a multiple regression with dummy variables, is it really necessary to include an intercept term in the design matrix? By dummy variables, I mean indicator variables; a one in the ...
49 views

Test whether variables follow the same distribution

If you want to test whether two variables follow the same distribution, would it be a good test to simply sort both variables, and then check their correlation? If it is high (at least 0.9?), then the ...
17 views

comparing AIC (or BIC or whatever) between different SETS of models

Suppose I have $m$ competing models. Suppose also that I could classify these models into $s$ sets. For example, I could classify models of migration behavior conditional on climatic conditions by the ...
32 views

Alternatives to the Baron-Kenny approach to modeling mediation

I'm about to open the door to a very thorny issue in the social sciences. How does one correctly model and test hypotheses about mediating variables using observational data? I'm familiar with the ...
59 views

How do you explain 'co-integration' to determine spurious regression to a fairly new time series student?

I would appreciate it if someone could explain the concept of spurious regression intuitively / without it being too technical. So far the student understands that spurious regression is basically ...
28 views

Maximum likelihood parameter estimates for Kalman filter with time-varying state transition

I'm currently studying Kalman filter, and the model I'm trying to fit is a uni-variate regression: $Y_t = \beta_t \mathbf{X_t} + v_t$ $\beta_t = \beta_t-1 + w_t$ where $v$ and $w$ are both ...
62 views

Interpretation of a Durbin-Watson test?

I have calculated a Durbin-Watson test and got as far as \eqalign{ d&=2.207551844, \\ dL&= 1.6164, \\ dU&= 1.7896. } I want to test $$H_0 \gt 0,\ H_1 \le 0.$$ However, I do not ...
40 views

Is there any Python equivalent of R's biglm?

I have used biglm in R and found it very useful. Now I need the same type of functionality in python. Any ideas? I have seen that patsy/statsmodels has an ...
31 views

Change point analysis

Could someone please explain change point to me. I'm using the package in R, and I don't really understand what the different methods mean, the pros and cons of each, and I especially do not ...
10 views

Import Voozanoo data into R [migrated]

Voozanoo allows exporting the data in various formats. What's the best way to import the data into R? I tried the CSV export, it worked, but extracting the codes and values of categorical variables ...
10 views

What's the difference between a feedback loop and a bidirectional path?

I had always thought that the relationship between x and y here was a bidirectional path. However, I note that Kenny at http://davidakenny.net/cm/iv.htm describes it as a feedback loop. That makes ...
63 views

Understanding bootstrap method for confidence interval of correlation coefficients

Please correct me where I'm wrong: My understanding of bootstrapping is that it is a way to estimate the distribution of some statistic (mean, standard error, Pearson's correlation coeff, etc), ...
40 views

How to fit a model with lagged variables

I am trying to fit a model with lagged variables. The problem is: In a big classroom with windows open, the outside temperature, humidity and solar activity will lead to variation in the ...
35 views

Use Random Forest model to make predictions from sensor data

say I have a sensor that measures temperature, pressure ++, and want to use this data to predict some quantity "A". If I use multivariate regression, I can simply implement a model of the form ...
37 views

How to plot a “differential word cloud” in R?

I have a questionnaire with one "open" text box, and 20,000 responses. I'm not planning to read all of them, but I'm thinking of interesting things to do with them. A general tag cloud would not be ...
35 views

How to deal with a lot of plots in R [migrated]

I have a for loop which produces 60 plots. I would like to save all this plots in only one file. If I set par(mfrow=c(10,6)) it says : ...
20 views

Assessing Significance in Neural Networks

I'm trying to determine statistical significance of inputs on the dependent variable using neural networks. I'm trying to test the null hypothesis that the partial derivatives are equal to zero. I ...
41 views

Selection of lme models using AIC & appropriate random effects & variance structure

I am using three categorical predictor variables X1, X2, X3 and one continuous dependent variable Y, and I want to treat X3 as a random effect. The simplest model I could come with: ...
34 views

Can agresti-coull binomial confidence intervals be negative?

According to http://www.itl.nist.gov/div898/handbook/prc/section2/prc241.htm agresti-coull intervals cannot be negative, however using the formula from wikipedia as well as the binom.confint function ...
19 views

MR with dummy variables

I need to calculate MR but my data consists of many dummy variables. I had a question in my survey that asked for the budget/month. But instead of giving the option to fill in a value, I offered ...
6 views

Topic Extraction using Scikit. Get documents for the Topics

I was trying to get a NNF model work for Topic Extraction. SCIKIT code http://scikit-learn.org/dev/auto_examples/applications/topics_extraction_with_nmf.html# works fine. But what i wanted was ...
40 views

Distribution of p-values from multiple experiments

My experimental setup is the following: compute an optimal solution $S$ to problem $A$ on instance $I$, evaluate test statistic $f(S)$, compute $f(S_i)$ for $S_i$ $(0 \leq i \leq n)$ drawn from a ...
52 views

Statistical tests when each variable in a sample is a percentage

I am performing a temperature preference test in mice. Mice are placed into a chamber with one half of a chamber having a cold floor and the other half having a warm floor. Mice spend a specific total ...
24 views

How to interprete TraMineRs results of disstreedisplay and seqtreedisplay

I am not quite sure what the differences are between the outputs and results of disstreedisplay and seqtreedisplay. Maybe you ...
11 views

deviding a storing a file as different vectors [closed]

I have a file with 3 columns how can i read the file and then save the third column’s values in different vectors depends on the first and second columns. for example in this example i need to save ...
56 views

Outline of benefits/costs of using Bayesian rather than Frequentist OLS and time-series?

I'm reading up on Bayesian techniques for Linear models and time series. While the texts are great at teaching the theory I would like to get a better handle on the pro's/con's of Bayesian analysis vs ...
48 views

Sample size with respect to prediction in classification and regression

With respect to hypothesis testing, estimating samples sizes is done through power, and it is intuitive that increasing the same size increases the precision of estimated effects. But what about ...
36 views

Testing Spearman's rho between-groups

I am analysing ordinal, non-normally distributed dependent measures using Spearman's rho. Specifically, we have an independent groups design, and I have found a significant relationship between the ...
19 views

Upper bound for the Cardinal of the Active Set in Lasso

I am searching for a proof to: With probability tending to one, we have that the cardianl of the active set in the Lasso estimator is bounded by $C\frac{n}{\lambda_n^2}$, ($C$ is some constant) i.e.; ...
91 views

The way an MA(q) model works

I am trying to understand the way MA(q) models work. For this purpose I have created a simple data set with only three values. I then adapted a MA(1) model to it. The results are shown below: ...
37 views

Identifying argmax result in information theory

I'm reading through a thesis at the moment which uses a "well known result from information theory", namely $\mathrm{argmax}_\mathbf{g}\,\mathbf{f}\,\mathrm{log}\,\mathbf{g} = \mathbf{f}$, for two ...
23 views

Visualization and navigation through a Pareto front

I've recently extended my genetic algorithm in such a way that it constructs a Pareto front, instead of weighing the different quality dimensions. The quality dimensions are not related to 'spacial' ...
17 views

Requirements for Evaluation function in evolutionary algorithms

For a publication I'm looking for references for generic requirements of evaluation/fitness functions in evolutionary (more specifically genetic) algorithms. I could come up with some requirements ...
26 views

Scikit-learn reports memory error when fitting Gaussian process model

I want to fit a Gaussian Process with about 50,000 training examples and 130 features using Scikit-learn. Right now, I only have 1 theta hyperparameters as I run the process with all defaults. But I ...
29 views

Shapiro test on replicated values

I have a distribution of frequencies (1000 data points) expressed as %. The list of data looks like this: 3.10% 1.80% 1.70% 1.70% 1.60% 1.60% 1.50% I would like ...
32 views

A function like lmer?

Can you suggest me any random effect linear model in R? At the moment I am using lmer, but I would like to know if there is any other similar function. Thank you
In McFadden - Analysis of Qualitative Choice Behavior, Axiom 3 (Irrelevance of Alternative Set Effect) states: The function $V(s,x,z)$ determining the selection probabilities in \$P(x|s,B) =\ ...