Can someone please give me a pointer here. I have two matrices matA A B C 1 5 2 4 2 2 4 3 3 1 2 4 matB A B C 1 TRUE FALSE TRUE 2 FALSE TRUE TRUE 3 FALSE FALSE FALSE how do I extract all the values from matA where the coresponding entry in matB == TRUE (or FALSE), perferably in vector form. Many thanks tom