performance of apply
Peter Dalgaard BSA
29 May 1998 18:04:30 +0200
Luke Tierney <email@example.com> writes:
> > > That is, the computation of the sums of the rows of a 10000x10 matrix
> > > with apply takes about 100sec on average, where a simple for-loop does
> > > the same job in about 2sec.
> It looks like M1 and M3 are O(n^2) but M1 is O(n). I see where that
> comes from in M3, but it surprises me for M1.
Oh, dear. Looking at apply, we have right in the middle of it:
for (i in 1:d2) ans[[i]] <- FUN(array(newX[, i], d.call,
Assignment to the tail of a very long list...
I think I'm beginning to understand why Ross keeps talking about
generic vectors. Either that or we need to add some low-level list
primitives to the language.
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
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