[R] Adding duplicates by rows

[Chuck Cleland]

Serguei Kaniovski wrote:
> Hi,
> 
> I am trying to add duplicates of matrix "mat" by row. Commands
> 
> subset(mat,duplicated(rownames(mat)))
> 
> or
> 
> mat[which(duplicated(rownames(mat))),]
> 
> return only half of the required indices. How can I find the remaining
> ones, ie the matches, so that I can add them up?

mat <- matrix(runif(70), ncol=5)
rownames(mat) <- c("Z", rep(LETTERS[1:6], each=2), "G")

  There is probably a more elegant way, but this seems to do what you want:

mat[rownames(mat) %in% names(which(table(rownames(mat)) > 1)),]

  Also, have you considered aggregate()?

aggregate(mat, list(ROW = rownames(mat)), sum)

> Thanks,
> Serguei
> 
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> 
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-- 
Chuck Cleland, Ph.D.
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