Filter matrix rows depending on values in a second matrix

Question

Given a 2x3 matrix x and a 4x2 matrix y, I\'d like to use each row of y to index into x. If the value in x i

Answer 1

This can be easily vectorized as follows (see sub2ind):

y = y(x(sub2ind(size(x), y(:,1), y(:,2)))==-1,:);