[R] Adjusting p values of a matrix

January Weiner january.weiner at mpiib-berlin.mpg.de
Mon Apr 4 17:02:28 CEST 2011

Dear all,

I have an n x n matrix of p-values. The matrix is symmetrical, as it
describes the "each against each" p values of correlation

How can I best correct the p values of the matrix? Notably, the total
number of the tests performed is n(n-1)/2, since I do not test the
correlation of each variable with itself. That means, I only want to
correct one half of the matrix, not including the diagonal. Therefore,
simply writing

pmat <- p.adjust( pmat, method= "fdr" )
# where pmat is an n x n matrix

...doesn't cut it.

Of course, I can turn the matrix in to a three column data frame with
n(n-1)/2 rows, but that is slow and not elegant.


-------- Dr. January Weiner 3 --------------------------------------
Max Planck Institute for Infection Biology
Charitéplatz 1
D-10117 Berlin, Germany
Web   : www.mpiib-berlin.mpg.de
Tel     : +49-30-28460514

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