# Tagged Questions

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### Multidimensional Scaling in R with Spearman's Rank Correlation

I'm new to MDS, but I found some good starter code here (http://mhermans.net/static/postdata/r-examples/neighbours-mds/neighbours-mds-example.html) and which I borrowed for below. The code works fine, ...
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### Bayesian method to compare correlations

I have read up on Bayesian methods enough now to feel that I would rather use Bayesian analysis over Frequentist, the trouble now is finding the correct tools... I have data from an experiment with ...
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### Calculating correlation coefficient

a <- c(10,11) b <- c(2,3) The covariance (C) betweena and ...
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### How to check if two variables are dependent given a third variable?

In R, I have a dataset of many variables and based on correlation matrix I see that some of the variable are correlate with the others. For simplicity, let's assume ...
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### How can I look for a correlation between dependent variables in a repeated-measures/within-subjects design?

I have a 2x3 within-subjects design, with two different dependent variables (DVs). I would like to know if the two DVs are correlated or not. Here is an example of what the data look like, e.g. a ...
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### Permutation test of meta-analysis : correlation coefficient

I am going to estimate False Discovery Rate using permutation tests. To my knowledge, several R packages are applicable for multiple testing. I have several independent datasets for meta-analysis. ...
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### Dependency of a third factor in a correlation between 2 continuous variables?

I'm studying the correlation between 2 continuous variables (A~B), the first is an independent measured variable (A), the second one is a dependent estimated variable (B). I'd like to know i) if the ...
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### How to identify variable (from many variables) which is able to discriminate between groups?

I currently have a data frame with 98 observations and 107 variables. All of the variables are numeric, but one variable is binary (yes or no). My goal is to determine which correlation and/or ...
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### R correlation between two time series analysis

This is my very first post on CV so comment if I can improve my post. I have two webs that sell very similar products and also have a very similar group of customers. I was trying to prove that ...
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### maximum correlation between two correlation matrices in R

How to estimate maximum observable correlation between two correlation matrices? I need this in order to correct the observed correlation coefficient between two correlation matrices I have ...
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### Why is Mantel's test preferred over Moran's I?

Mantel's test is widely used in biological studies to examine the correlation between the spatial distribution of animals (position in space) with, for example, their genetic relatedness, rate of ...
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### Is there autocorrelation in volatile series?

I read in many books or notes online that (1)volatile series do not differ significantly from white noise and that (2)their squared values will exhibit correlation. Although I agree with (2), I can't ...
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### Covariance and correlation matrix comparison

I am aware that this question may be too broad and that answers are scattered in various posts, but i need concise and organized answer. My dataset consists of linear measurements of cranial ...
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### What statistical test is appropriate for correlations within repeated measures?

We have $N$ individuals measured repeatedly in time. For each individual, at each measurement, we measure the values of two variables: $A$ and $B$. The number of measurements per individual might ...
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### How to filter only positive correlations on R? [closed]

Is it possible to filter only positive correlations on R? The point is to make clusters of time series using the correlation as a distance measure, but without clustering the series that have ...
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### gls R correlation setting form to default

Just looking for some instruction please. I wish to set an autoregressive correlation within a gls model. I am having trouble understanding this part of the syntax ...
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### How to test whether variables are more frequently associated than expected by chance?

I have this presence/absence matrix (S2 is missing on purpose). ...
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### Bootstrap on correlation coefficients in R [closed]

For each round of bootstrapping (say $n=1000$), I would like to select the genotypes (the columns) at random without replacement from the original dataset. With this I would like to form two groups ...
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### Create 3 correlated variables with pre-specified correlations [duplicate]

I start with a vector of random numbers sampled from a normal distribution: R<-rnorm(100, mean=0, sd=30) I would now like to create 3 variables that are ...
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### Create variables with pre-specified correlation

I have a vector: a<-rnorm(100) I would like to create 5 variables that are correlated with a to a different extent. For ...
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### Significance of adjacency in correlation matrix with ordered variables

The following values are from the Discrete module in BayesTraits. Each value in the matrix is the difference in log-likelihood values between a 4-parameter model of independent evolution and an ...
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### Correlation or independence on contingency table for large N

I have a dataset with about 35,000 individuals described by around 15 categorical variables. I'm trying to study the independence / correlation between these 15 categorical variables. My first idea ...
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### Definition of autocorrelation time (for effective sample size)

I've found two definitions in the literature for the autocorrelation time of a weakly stationary time series:  \tau_a = 1+2\sum_{k=1}^\infty \rho_k \quad \text{versus} \quad \tau_b = ...
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### How to test the effect of variable on spatial distribution of points in R

I'm trying to find statistical test (or procedure) which is able to discover patterns in spatial distribution of points. I sketch the problem by giving the example about position of bird territories ...
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### Finding correlations in longitudinal data analysis

We are doing research on video lecture watching. We offer a course which lasts four 5 weeks, and there are 9 or 10 videos in each week. We organize group-watching activities. A group usually is ...
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### R: estVar and cor

I have a problem when estimating a multivariate Regression Model. I know that cor(y1, y2) is strongly positive but when I am trying to estimate a regression model ...
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### Are two Pearson correlation coefficients different?

I am aware of this question here, which mine was listed as a duplicate of, but it does not fully answer my question. It did however help me progress a little further so thanks, I couldn't find it ...
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### Within-subject correlation before deciding on correlation structure in GEE

I want to have a look at the correlation coefficient for repeated measures in $x$ number of individuals. This will help me chose which correlation structure will best fit in GEE (Generalized ...
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### Which kind of test is most suitable for comparing correlations of 3 methods?

I have a R data frame like this: ...
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### Why am I not getting a symmetrical correlation matrix in R?

I am trying to obtain the correlation between two matrices of equal dimensions. I have used both column by column correlation and the canonical correlation but I don't get a symmetrical correlation ...
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### Correlations of correlations using 3 data sets

I'm interested in how 14 environmental parameters co-vary with other environmental parameters and whether they show the same patterns in 3 regions. So 1st, I made a pairwise correlation table of the ...
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### Correlation of Fixed Effects in lmer

I'm a psycholinguistics student with few knowledge in statistics and I have some doubts about a Correlation of Fixed Effects in lmer function (lme4 package). So, if my question is stupidâ€¦ hummmâ€¦ I'm ...
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### How to check for a relationship between water bacterial levels

I have a set of data: http://pastebin.com/KHLKD8XB which is based on TVC (total viable counts - i.e., numbers of bacteria) from water going into a machine (BM), water taken from the machine (IM) ...
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### What is the best way of presenting a correlation? (in R)

I have two variables which show significant correlation (Spearman). I would like to graphically show the strength of the relationship, much like showing a linear regression fit with confidence bands. ...
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### Which variables are driving correlations within groups

I'm running an analysis on a few data sets that each typically have 100-200 cases measured across 120-160 variables - something similar to looking at gene expressions. Each variable is a non-centered ...
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### Correlation with different vector length - same time period

I have a data set containing equity price information on a tick by tick basis. I would like to calculate the correlation in R, which isn't a hassle. But the vectors are of different length due to one ...