--- Roger Hui <[EMAIL PROTECTED]> wrote: > Better to just map i and j and values separately > (perhaps i,.j and value as two map files), and apply your > iterative methods to these.
Or maybe three mapped files: i, j, values. Then access to the matrix is simply relational. See http://www.jsoftware.com/jwiki/DB/Flwor i.3 4 NB. matrix 0 1 2 3 4 5 6 7 8 9 10 11 (#: i.@(*/)) 3 4 NB. index odometer 0 0 0 1 0 2 0 3 1 0 1 1 1 2 1 3 2 0 2 1 2 2 2 3 'r c'=. |:(#: i.@(*/)) 3 4 v=. ,@i. 3 4 r,.c,.v NB. relational form 0 0 0 0 1 1 0 2 2 0 3 3 1 0 4 1 1 5 1 2 6 1 3 7 2 0 8 2 1 9 2 2 10 2 3 11 1 = r NB. row 1 mask 0 0 0 0 1 1 1 1 0 0 0 0 v #~ 1=r NB. SQL: select v where r=1 4 5 6 7 1 2 =/ r NB. rows 1 2 mask 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 v #~ 1 2 =/ r NB. rows 1 2 value 4 5 6 7 8 9 10 11 1 = c NB. column 1 mask 0 1 0 0 0 1 0 0 0 1 0 0 v #~ 1 = c NB. etc ... 1 5 9 v #~ c = 1 1 5 9 1 3 =/ c 0 1 0 0 0 1 0 0 0 1 0 0 0 0 0 1 0 0 0 1 0 0 0 1 v #~ 1 3 =/ c 1 5 9 3 7 11 (t#r),.(t#c),.v#~t=. 0=4|v NB. 4 multiple 0 0 0 1 0 4 2 0 8 (~.r) ,. r+//.v NB. sum by rows 0 6 1 22 2 38 +/"1 i.3 4 6 22 38 ____________________________________________________________________________________ Looking for last minute shopping deals? Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
