skewers(X, Y, nsim=100, method=NULL)
method=NULL
then the correlation will be compared to the correlation between random vectors; however this test has type I error substantially above the nominal level for ostensibly random matrices. Other values of method
will be passed as covMethod
to genPositiveDefMat
for a more robust hypothesis test (see below). Recommended values include "unifcorrmat"
.Cheverud, J. M. & Marroig, G. (2007) Comparing covariance matrices: Random skewers method compared to the common principal components model. Genetics & Molecular Biology, 30, 461--469.
Revell, L. J. (2012) phytools: An R package for phylogenetic comparative biology (and other things). Methods Ecol. Evol., 3, 217-223.