I'm working with "passive subtraction": tbl2=. 2 -~/ \"1 tbl
However, I need to create a series of such subtractions where 2 columns at a time are still used but where the distance between the columns subtracted can vary. For simplicity, I'll just use a list (rather than table) of numbers to show what I'm after: lst=. 3 8 12 5 7 13 11 15 14 10 7 11 The first result would be the same as above, where the subtracted elements are 1 apart, that is, adjacent (I'm showing the subtractions rather than the results, but, of course, I really want the subtraction results) (#lst1 is 11): lst1=. 8-3 12-8 5-12 7-5 13-7 11-13 15-11 14-15 10-14 7-10 11-7 The next result would do the same passive subtraction, only on elements that are 2 apart (rather than adjacent) (#lst2 is 10): lst2=. 12-3 5-8 7-12 13-5 11-7 15-13 14-11 10-15 7-14 11-10 The third result would do the same passive subtraction, only on elements that are 3 apart (#lst3 is 9): lst3=. 5-3 7-8 13-12 11-5 15-7 14-13 10-11 7-15 11-14 And so on. The tenth result's elements are 10 elements apart (#lst10 is 2): lst10=. 7-3 11-8 And the eleventh result's elements are 11 elements apart (#lst11 is 1): lst11=. 11-3 It would seem logical that perhaps there's a single algorithm with a variable along the lines of i.(#lst-1) or else the distance apart of the subtracted elements could be the x argument of a verb (including an i.(#lst-1) type of argument), where lst is the y argument. A table produced by an i.(#lst-1) type of variable or argument should be zero- filled. (I don't need it for my particular application, but I presume that if the y argument were a table rather than a list, then the end result would be a table of tables.) This whole thing has a very practical application to something I'm working on, and I would appreciate any help that anyone has to offer. Thanks in advance for your assistance! Harvey ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
