[R] optimal way to compute matrix subtotals?

From: Werner Wernersen <pensterfuzzer_at_yahoo.de>
Date: Fri 12 May 2006 - 19:48:45 EST


I have large matrices, one column per variable and I have a vector of factors / grouping symbols. Then I am computing subtotals for the groups but it takes pretty long and thus I wanted to ask if there is a better way to do it or if this is already the best way: subTotals <- function(x, groupvec) do.call("rbind",lapply(split(x,groupvec),colSums,na.rm=T))

Thanks reading my question and any hints!  Werner                 

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