[R] Re: tapply for matrices

[Ott Toomet]

I have made a similar simple routine for my own purposes.  I have not
compared the speed.  Is there any good reason not to add something
similar to the base package, perhaps as a method for tapply?

Ott

----------------------------

tmapply <- function(X, INDEX, FUN=sum, ...) {
### tapply a function over a columns of a matrix
  tvapply <- function(X, ...) {
    ## apply the function for a (column) vector
    tapply(X, INDEX, FUN, ...)
  }
  apply(X, 2, FUN=tvapply, ...)
}
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