Hi all,
Suppose we have the following matrix
m <- matrix(c(1,2,3,2,1,3,3,1,2), ncol = 3, byrow=T)
where in each row each number occurs only once.
I'd like to define a permutation, e.g. 1 -> 2, 2 -> 1, 3 -> 3 and apply
it to the matrix. Thus, the following matrix should result:
m.perm <- matrix(c(2,1,3,1,2,3,3,2,1), ncol = 3, byrow=T)
i.e. each 1 should map to 2 and vice verse while 3 maps to itself. What
I've done so far is:
permutateMatrix <- function(mat, perm=NULL) {
values <- 1:NCOL(mat)
if (is.null(perm)) {
perm <- sample(values)
}
newmat <- replace(mat, sapply(values, function (val) which(mat==val)),
rep(perm, each=NROW(mat)))
return(list(mat.perm=newmat, perm=perm))
}
"perm" is the permutation vector: 1 maps to the first element of perm, 2
to the second and so on. Thus, for the example we would use
perm <- c(2,1,3)
all.equal(m.perm, permutateMatrix(m, perm)$mat.perm) # TRUE
What do you think of this solution? Are there more elegant ways of doing
that? Any comments appreciated.
Thanks + BR,
Thorn
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
