Ian, I best understood key after reading a book you edited ;-)
To summarize... http://www.jsoftware.com/jwiki/Doc/Articles/Play151 All the best, Ken -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Ian Clark Sent: Tuesday, May 17, 2011 5:09 PM To: Programming forum Subject: [Jprogramming] Aggregation I'm being lazy here. But I need a better answer than I can devil out myself. It occurs in a recent submission to Vector... I have an array like this (which may be unsorted, and can grow very large): 1 100 1 100 1 20 1 400 2 30 2 200 2 300 33 100 33 100 33 100 I want to collapse it to: 1 620 2 530 33 300 i.e. summing over subheadings. The original example had A B C in place of 1 2 33, but numbers will do, to save boxing. We don't know the full set of A B C ... in advance. Nothing to be assumed about the first column, except it is +ve integers. But I'm also interested in the case where the first column lies in the set: i.(n) for some n>0. In other words they can be squashed up. 1. There's simply got to be a "jem" to do it. Suggestions, please. - Transpose the array if you wish. Box it: 1 100 ; 1 100 ; 1 20 ; ... -whatever. - No, of course I don't want a looping solution :) 2. What do you call this process? I call it "aggregation" -- but I think the name differs across disciplines. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
