[R] Computing sums of the columns of an array

[Duncan Murdoch]

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