Say I have a boolean matrix ] map=. 3 4 $ 1 0 0 1 0 1 1 0 0 0 0 0 1 0 0 1 0 1 1 0 0 0 0 0
and 2 vectors of dimension equal to the 2 sides of the matrix m=. 'abc' [ n=. 'ABCD' I want a cross product for those 1 in the matrix, with result like this _2 ]\ 'aAaDbBbC' aA aD bB bC Is it possible to do it without explicit loops? The dimension of the matrix can be very large so that generating all cross products then eliminating is not an option. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
