reinvigorate iapply?

[r2evans]

On StackOverflow, a recent answer by G. Grothendieck mentioned an old email of yours about an idempotent apply. Have you (would you?) consider adding an iapply to your reshape package?

Perhaps simply:

iapply <- function (X, MARGIN, FUN, ...)  {
	dims <- c((1:length(dim(X)))[!(1:length(dim(X)) %in% MARGIN)], MARGIN)
	res <- apply(X, MARGIN, FUN, ...)

	if (length(dim(res)) == length(dims)) {
		aperm(res, order(dims))
	} else {
		res
	}	
}

(I added the ... to the apply call since I thought it was appropriate, otherwise this is verbatim from your 2006 email.)

Edit: 121d0ff suggests functions were moved to plyr (I find no use of it there), and 6058c3b is what actually removed iapply with no direct mention of why it was removed.