Question

In MATLAB, I’d like to apply a function to every pair of column vectors in matrices A and B. I know there must be an efficient (non for) way of doing this, but I can’t figure it out. The function will output a scalar.

Answer 1

Try

na = size(A,1);
nb = size(B,1);
newvector = bsxfun(@(j,k)(func(A(j,:),B(k,:))),1:na,(1:nb)');

bsxfun performs singleton expansion on 1:na and (1:nb)’. The end result, in this case, is that func will be applied to every pair of column vectors drawn from A and B.

Note that bsxfun can be tricky: it can require that the applied function support singleton expansion itself. In this case it will work to do the job you want.