Why do you have to start with a non-sparse matrix? 1$.s;a;e builds a blank sparse matrix with the "full shape" s .
----- Original Message ----- From: June Kim <[EMAIL PROTECTED]> Date: Saturday, May 17, 2008 19:35 Subject: [Jprogramming] Re: sparse matrix from index/value pairs To: Programming forum <[email protected]> > 2008/5/18, June Kim <[EMAIL PROTECTED]>: > > Is there a more efficient way of getting sparse matrix from > index/value pairs? > > > > s > > 0 1 │ 1 > > 0 2 │ 10 > > 1 0 │ 2 > > 1 3 │ 100 > > (4&$.,.5&$.)s > > 0 1 1 > > 0 2 10 > > 1 0 2 > > 1 3 100 > > > > I'm thinking about some verb f that might satisfy(or something > similar):> > > s-:(4&$.,.5&$.)s > > Sorry for my typo: > > s-:f (4&$.,.5&$.)s > > > > > I can do that using amend, but I have to build up a blank > matrix of > > I mean, build a blank non-sparse matrix and amend it, and turn > it into > a sparse matrix. > > > the full shape in the first place. Are there more efficient > ways in > > time and space-wise? ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
