In R, correlation test between two columns, for each of the groups in a third column

Question

My data frame (g) contains 2 columns with continues data and other columns with categorical data. I want to test for correlations between the 2 continues variables, in diffe

Answer 1

I think you want this inside of function r:

if ((length(x[[1]]))>2)
    cor.test(x[[1]],x[[2]],use="pairwise.complete.obs")[3:4] else NA

x[[1]] is a vector, whereas x[[1]][1] is a single element of that vector. You clearly want vectors for cor.test and not single elements.

In addition, a vector has a length but nrow is not appropriate.

The error that you get is a result of nrow(x[[1]][1]) evaluating to NULL, so nrow(x[[1]][1]) > 2 evaluates to logical(0). The argument to if should be a logical of length 1.