Sorry folks I posted the code with a bug in approach 2. aarrrhh. it should have
been...
## Approach 2: loop on k2
output2 = matrix(0,nrow=n,ncol=k2)
pt2 = proc.time(for (i in 1:k2) output2[,i] = rowSums( m1*(m2[,rep(i,3)]) ))
I haven't seen any other response yet (after 8 hours!) but doesn't:
Hi
I want to sum over one of the dimensions of a n x k1 x k2 array in
which each column is the product of the corresponding columns from two
matrices with dimensions n x k1 and n x k2. I can see two approaches:
a loop on k1 and a loop on k2. But I cannot figure a solution that
avoids the loop? Is
