[R] speeding up a special product of three arrays

From: Giuseppe Paleologo <paleologo_at_gmail.com>
Date: Thu, 08 May 2008 17:20:52 -0400

I am struggling with R code optimization, a recurrent topic on this list.

I have three arrays, say A, B and C, all having the same number of columns. I need to compute an array D whose generic element is

D[i, j, k] <- sum_n A[i, n]*B[j, n]*C[k, n]

Cycling over the three indices and subsetting the columns won't do. Is there any way to implement this efficiently in R or should I resign to do this in C?



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