($tst) #: I. , tst Works for any rank array, not just matrices.
----- Original Message ----- From: "Sherlock, Ric" <[EMAIL PROTECTED]> Date: Wednesday, June 11, 2008 16:56 Subject: [Jprogramming] find row and column indices To: Programming forum <[email protected]> > In separate thread I needed to find the row and column indices > of 1s in a rectangular array. > > tst=: _99&".;._2 (0 : 0) > 0 0 0 1 0 0 > 0 0 0 0 0 0 > 1 0 0 0 0 0 > 0 0 0 1 0 0 > 0 0 0 0 0 0 > 1 0 0 0 0 0 > ) > > indices tst > 0 3 > 2 0 > 3 3 > 5 0 > > I came up with the following but feel I'm probably missing > something (much) simpler? > > indices=: (1 , {:@$) *"1 [: (<. ,. 1&|) {:@$ %~ [: I. , ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
