Re: [R] Computing sums of the columns of an array

From: Duncan Murdoch <murdoch_at_stats.uwo.ca>
Date: Sat 06 Aug 2005 - 02:24:08 EST

On 8/5/2005 12:16 PM, Martin C. Martin wrote:
> Hi,
>
> I have a 5x731 array A, and I want to compute the sums of the columns.
> Currently I do:
>
> apply(A, 2, sum)
>
> But it turns out, this is slow: 70% of my CPU time is spent here, even
> though there are many complicated steps in my computation.
>
> Is there a faster way?

You'd probably do better with matrix multiplication:

rep(1, nrow(A)) %*% A

Duncan Murdoch



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