2
votes
1answer
13 views

Small number of points driving correlation

I am currently looking at trying to find high correlations in a series of data. I initially just thought I could check the correlation of the data and choose those with the highest correlation but ...
2
votes
1answer
54 views

Value of r, i.e. correlation coefficient, of data points on a horizontal straight line

1) If we use the formula $$r = \displaystyle \frac{\displaystyle\sum_{i=1}^n \left( x_i - \bar{x} \right) \left( y_i - \bar{y} \right)}{\sqrt{\displaystyle \sum_{i=1}^n \left( x_i - \bar{x}\right)^2 ...
0
votes
2answers
32 views

Correlation between unordered categorical variable and numerical variables

I have a dataframe with many observations and many variables. Some of them are categorical (unordered) and the others are numerical. I'm looking for associations between these variables. I've been ...
2
votes
1answer
50 views

Interpret Pearsons correlation output from R

I have conducted Pearson's correlation in R and need help interpreting the results. ...
0
votes
0answers
22 views

Correlation tests – multivariate correlation matrix?

I just got comments from a reviewer to a submitted article and didn't understand what I should do very well. Here are the tests I performed: We first used principal components analysis (PCA) to ...
-1
votes
0answers
53 views

Finding correlations among many variables

I have 60 variables (each has 100 numerical data points) which could go up as high as 200 variables. I would like to run a test and see if there are any relationships between them. E.g, if variable A ...
1
vote
0answers
9 views

Conditional distribution of serial correlated errors

So I have a gls model, using the nlme package. It has a CAR1 correlation structure. Is it right that the conditional distribution of it's errors will be: $$ \varepsilon_i | \varepsilon_j \sim ...
2
votes
1answer
24 views

is it possible to check Czuprow's coefficient of the convergence in R package?

just wondering - is it possible to calculate Czuprow's coefficient of the convergence in R package? if so, is there some dedicated package for that purpose? thanks in advance
2
votes
0answers
67 views

Interpolating time series wind data using correlation

Is there a way to use correlation to interpolate missing data? I know the wind speed in 6 locations every hour. This shows the correlation between the separate locations. Hourly Data I know the wind ...
3
votes
1answer
133 views

Generating a correlated data matrix where both observations and variables are correlated

I am trying to generate a simulated data matrix that is correlated by both observation and variable directions. So far I know how to do this for variable x variable. ...
1
vote
0answers
36 views

Correlation between two variables measured in separate experiments in R

I'm trying to show a correlation between growth in a petri dish of some fungi and its effect on a plant. I have ten strains of fungi which I tested in the plant and in petri dishes. I can put data ...
0
votes
0answers
26 views

Not getting correct lag values in output

I am using R to calculate lagged correlation. Instead of getting lag values -20 to 20, I am getting the following values: ...
8
votes
1answer
26 views

When should I use each of these methods to calculate correlation?

I am using R for data analysis. R provides a corr function for calculating the correlation. This function provides three different approaches/algorithms to ...
2
votes
1answer
118 views

What does this residuals versus fitted plot mean about my model?

I have a model that attempts to predict a nation's quality of life index by it's moral indifference to contraception and moral rejection of gambling. Initially the model contained several predictors, ...
2
votes
2answers
105 views

Building the connection between cosine similarity and correlation in R

According to some articles (e.g. here) correlation is just a centered version of cosine similarity. I use the following code to calculate the cosine similarity matrix of the column vectors of a matrix ...
2
votes
1answer
88 views
2
votes
2answers
133 views

Why is the Pearson correlation 1 when only two data values are available?

I am trying to obtain a Pearson correlation between 6 different variables (represented by columns in the matrix below) with two datapoints each (rows). This is the matrix: ...
0
votes
1answer
50 views

Investigating relationships between variables- multiple and simple linear regression

please help a sociologist struggling to get to grips with R and statistics in general..! I've got a data set with 11 variables. I need to investigate the possible relationships between one of the ...
2
votes
1answer
110 views

How important is the correlation coefficient's variance in linear regression?

R doesn't return the correlation coefficient's variance (or standard error) when coding summary(linmod), linmod being a linear ...
0
votes
1answer
46 views

Bivariate random variable with R [closed]

I am trying to transform this Matlab code into R. My goal is to generate a bivariate random variable with a pre-specified correlation. The code uses the idea of t-copula. I can't figure out how to ...
0
votes
0answers
25 views

Choosing the best time series for forecasting

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. Currently I am simply using X out of Y time ...
1
vote
1answer
67 views

Multiple comparisons for correlation matrix?

Does the computation of an N x N correlation matrix for N unrelated variables require multiple comparisons correction for all the computed pairwise correlations (assuming each computed correlation is ...
1
vote
0answers
41 views

How to measure/clarify a possible relationship between two spatial points using R

I'm quite new to the area of spatial statistics, but I'm very interest in some general principles. The last two weeks I've created an example dataset, which contains three datsets. A dataset of ill ...
0
votes
0answers
17 views

Influence of using differences or means in order to find correlations

I have a big dataset I want to find correlations in. So far I have been unsuccessful. I'm wondering whether it would be a good idea to either: Take the average of all neighboring entries in all my ...
0
votes
0answers
60 views

Low number of replicates DGE analysis

I am using DESeq for DGE analysis. I have STRANDED RNA-Seq data for 4 developmental stages with no replicates. To have a more reliable DGE I should have replicates and so I obtained (from another lab ...
1
vote
0answers
29 views

How to predict the model fit of a particular % of a sample?

I have a large number of projects (about 300). Each project contains a set of test cases. Each test case can result in a success or a failure. The dataset looks like this. Original: ...
1
vote
2answers
123 views

How to determine the correlation between 2 time series while controlling for a 3rd?

I would like to determine the relationship between two variables after controlling for a third. Specifically, I want to know if the prices of mercury and gold over time are correlated with each other ...
1
vote
0answers
86 views

Correlation between the proportion derived from the data of different size

I want to obtain a correlation between the accuracy of two linguistic features by language learners. The learners wrote a number of essays, and the number of correct and incorrect use of the article ...
3
votes
1answer
126 views

Generate two variables with precise pre-specified correlation

I want to generate two variables with (pseudo-) random numbers with an exact pearson's r. How do I do that? Python and/or R solutions would be nice! I am able to generate random data that ...
2
votes
0answers
697 views

How to test and avoid multicollinearity in mixed linear model?

I am currently running some mixed effect linear models. I am using the package "lme4" in R. My models take the form: ...
0
votes
1answer
96 views

Generating correlated distributions with a certain mean and standard deviation?

Given a distribution A with a mean of $\mu_1$ and standard deviation of $\sigma_1$, how can I generate: Distribution B with a mean of $\mu_2$ and standard deviation of $\sigma_2$ and a correlation ...
1
vote
0answers
80 views

Large discrepancy between confidence intervals for correlation coefficient using bootstrap and Fisher's Z transform

I found that the default confidence intervals provided by cor.test (Fisher's Z transform according to the help) are quite different from the nonparametric boostrap confidence intervals for the below ...
6
votes
1answer
303 views

Variables lack correlation, but have pattern

Below is the graph of two variables, X and Y, each representing count data. N=348. Note the scales of the axes: Y is very approximately lognormal, but X has no decent fit (including Poisson, ...
0
votes
0answers
255 views

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, ...
2
votes
0answers
95 views

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 ...
0
votes
1answer
110 views

Calculating correlation coefficient

a <- c(10,11) b <- c(2,3) The covariance (C) betweena and ...
2
votes
0answers
58 views

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 ...
2
votes
1answer
211 views

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 ...
2
votes
0answers
108 views

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. ...
0
votes
0answers
54 views

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 ...
1
vote
3answers
304 views

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 ...
1
vote
0answers
683 views

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 ...
0
votes
0answers
128 views

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 ...
21
votes
1answer
889 views

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 ...
0
votes
1answer
39 views

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 ...
0
votes
1answer
215 views

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 ...
1
vote
0answers
71 views

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 ...
1
vote
0answers
69 views

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 ...
0
votes
0answers
36 views

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 ...
1
vote
1answer
41 views

How to test whether variables are more frequently associated than expected by chance?

I have this presence/absence matrix (S2 is missing on purpose). ...