II have come across a feature of J that I didn't expect. When I add rows of a matrix, I use +/"1
a 1 2 3 4 1 2 3 4 1 2 3 4 +/"1 a 10 10 10 And columns, +/"2 a 3 6 9 12 By chance, I happened to 'misplace' insert and got an unexpected result +"1/a 3 6 9 12 which is the addition of the columns. However, +"2/ a 3 6 9 12 Now take another matrix b b 1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4 I would like to multiply every row of b by every row of a, but a*/"1 b |length error | a */"1 b While a*"1 / b 1 2 3 4 2 4 6 8 3 6 9 12 4 8 12 16 1 2 3 4 2 4 6 8 3 6 9 12 4 8 12 16 1 2 3 4 2 4 6 8 3 6 9 12 4 8 12 16 Which appears to work. I am obviously missing something with rank and insert. Could someone enlighten me? Any insight is much appreciated, as always. Bob ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
