2008/5/18, Roger Hui <[EMAIL PROTECTED]>: > Why do you have to start with a non-sparse matrix?
Please consider the sales example I posted here earlier. I can calculate the indexes and the sum of sales for (area, model) pair, like how I did in my script. Using those two vectors(indexes, values), I want to get a sparse matrix, for its space and time-efficiency for furthur analysis. > 1$.s;a;e builds a blank sparse matrix with the "full shape" s . > Thanks. Now I can amend the blank sparse matrix with indexes and values vectors. > > > ----- Original Message ----- > From: June Kim <[EMAIL PROTECTED]> > Date: Saturday, May 17, 2008 19:35 > Subject: [Jprogramming] Re: sparse matrix from index/value pairs > To: Programming forum <[email protected]> > > > 2008/5/18, June Kim <[EMAIL PROTECTED]>: > > > Is there a more efficient way of getting sparse matrix from > > index/value pairs? > > > > > > s > > > 0 1 │ 1 > > > 0 2 │ 10 > > > 1 0 │ 2 > > > 1 3 │ 100 > > > (4&$.,.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 >
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