On 03/20/2012 01:40 PM, Hervé Pagès wrote: [...] > This maybe would be fast enough if you don't have too many columns: > > viewColSums <- function(x) > { > sapply(seq_len(width(x)[1L]), > function(i) > sum(subject[start(x)+i-1L])) sum(subject(x)[start(x)+i-1L])) of course... H.