acp=: 1 : '; (<"0 x) ,"0 L: 0 m <@#"1 y' 'abc' map acp 'ABCD' aA aD bB bC
-- Regards Igor On Tue, 21 Sep 2021, 19:37 bill lam, <[email protected]> wrote: > 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
