> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of debra ragland
> via R-help
> some sample data
> p<-matrix(c(rep(c(F,T,F),3), rep(c(T,F,T),3), rep(c(T,T,F),3),
> rep(c(F,F,T),3)))
i) Something wrong with p, here; it's a single column matrix. did you mean
p4<-matrix(c(rep(c(F,T,F),3), rep(c(T,F,T),3), rep(c(T,T,F),3),
rep(c(F,F,T),3)), ncol=4)
? (I changed the name for later)
ii) You don't need split(), just ordinary indexing. For example
wilcox.test(pc1.eigv[ p[1,] ], pc1.eigv[ !p[1,] ] )
> I am now interested in using the same vector and (logical)matrix run the
> wilcox.test
> only this time I would like information about pairs of rows
ii) 'fraid that's not specific enough. How will you select the pairs (what row
indexes will you want) and do you intend to test one row in each pair against
the other or concatenate the TRUE and FALSE sets from the rows and then test
TRUE vs FALSE?
> After some searching I thought that perhaps the combn function would help me
> (i.e. combn(p)) for the same loop but I get an error.
iv) Did you mean
rowpairs <- combn(length(p), 2) #or combn(nrow(p), 2) if p is really a matrix
?
If you did, that generates a 2 x p matrix so your row pairs would be accessed
via
rowpairs[, i]
v) You don't need a loop either. Consider
#Set up a function to do the donkey work on a particular
#pair of row indices:
rptest <- function(rows, p, pc1) {
#Simplify later extraction by extending pc1.eigv:
pc2 <- rep(pc1, 2)
#extract and concatenates the two rows of the TRUE/PALSE matrix p
select <- as.vector( p[rows,] )
#Combine the two in a wilcox test
wilcox.test(pc2[ select ], pc2 [ !select ] )
}
rowpairs <- combn(nrow(p4), 2)
apply(rowpairs, 2, rptest, p=p4, pc1=pc1.eigv)
#Returns a list of wilcoxon tests of TRUE vs FALSE on all rows taken
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