[R] A slightly unorthodox matrix product.

[Rolf Turner]

Can anyone think of a sexy way of forming following "product"?

Given matrices A and B, both with m rows, form a 3 dimensional array C 
such that:

     C[i,j,k] = A[i,j]*B[i,k]

I *think* that the following does what I want.  (I keep confusing 
myself, so I'm not sure!)

library(abind)
xxx <- lapply(1:nrow(a),function(i,a,b){a[i,]%o%b[i,]},a=A,b=B)
do.call(abind,c(xxx,list(along=3)))

Is there a cleverer way?

cheers,

Rolf Turner

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