You have to do more than that. e.g.: v=: 100 [EMAIL PROTECTED] 0 bv=: 100 [EMAIL PROTECTED] 2
m=: 100 37 [EMAIL PROTECTED] 0 bm=: 100 37 [EMAIL PROTECTED] 2 vm=: (bv*v) +/ .* bm*m bvm =: bv +./ .* bm But what is the alternative? It seems to me that an "in-band" missing value indicator is like NaN , whose mathematical properties require very careful handling. e.g. What should the following be: missing*missing? missing^missing? /: 1 2,missing,4 ? (+/%#) 1 2,missing,4 ? Replace "missing" by NaN and you'd have the running-around- in-circles exercise that we went through. ----- Original Message ----- From: "Philip A. Viton" <[EMAIL PROTECTED]> Date: Friday, September 5, 2008 11:24 Subject: [Jprogramming] Re: data-munging in J To: [email protected] > > 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? ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
