[R] Re: tapply for matrices

Ott Toomet otoomet at econ.dk
Fri Oct 11 08:32:56 CEST 2002

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?



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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