Computing sums of the columns of an array
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