Wacek Kusnierczyk wrote:
> is your data a data frame or a matrix? do you want to compute the
> differences columnwise, i.e., for each column independently? consider
> this example:
>
> # generate and display dummy data
> (d = as.data.frame(replicate(3, sample(5))))
>
> # compute successive differences columnwise
> as.data.frame(apply(d, 2, diff))
> apply(as.matrix(d), 2, diff)
>
>
haven't noticed the sum part; you can apply colSums to the above
resulting data frame or matrix, e.g.:
colSums(apply(d, 2, diff))
vQ
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