Thanks, Roger (and also for the reminder that _ % _ is NaN : it must have been another edge-case that I was thinking of).
Anyway, maybe I'm missing something, but how would one implement the boolean suggestion when one was going to do, eg v (+/ . * ) mx where v is a vector and mx is a matrix (ie the matrix product of v and m)? Wouldn't this require you to do all calculations twice, once with the data and one for the boolean control?
------------------------ Philip A. Viton City Planning, Ohio State University 275 West Woodruff Avenue, Columbus OH 43210 [EMAIL PROTECTED] ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
