Thanks heaps Glenn for the programming tips. It's doing
exactly what I after.
Susan
----- Original Message Follows -----
From: Susan Olivia <[email protected]>
To: Susan Olivia <[email protected]>
Subject: Fwd: st: Matrix transformation
Date: Fri, 3 Apr 2009 16:40:23 -0700
> ---------- Forwarded message ----------
> From: Glenn Goldsmith <[email protected]>
> Date: Fri, Apr 3, 2009 at 4:08 PM
> Subject: st: Matrix transformation
> To: [email protected]
>
>
> Hi Susan,
>
> As far as I'm aware Stata/Mata don't really do sparse
> matrix storage, but you can otherwise replicate the
> behavior of sparse() with the following mata function:
>
> ********* Begin code **************
> mata:
> real matrix sparse(real matrix x)
> {
> real matrix y
> real scalar k
>
> y = J(colmax(x[,1]),colmax(x[,2]),0)
> for (k=1; k<=rows(x); k++) {
> y[x[k,1],x[k,2]] = y[x[k,1],x[k,2]] + x[k,3]
> }
>
> return(y)
> }
> end
> ********* End code ****************
>
> You can then call this either from within mata:
>
> y = sparse(x)
>
> or within stata:
>
> mata : st_matrix("y",sparse(st_matrix("x")))
>
> (in both cases assuming that your input matrix is called x
> , and output matrix is called y).
>
> HTH,
>
> Glenn
>
>
> "Susan Olivia" <[email protected]> wrote:
>
> Dear all,
>
> I would like to transform a say 4272 x 3 matrix (this
> matrix basically tells us the distance between each pairs
> of observation) onto 1068 x 1068.
>
> In MATLAB, this can be transformed using the following
> command:
>
> load GIS_4NN.txt;
> W4NN = sparse(GIS_4NN(:,1), GIS_4NN(:,2), GIS_4NN(:,3));
>
> Is there any equivalent command like the above in STATA?
>
> Any tips on this much appreciated.
>
> Thanks,
>
> Susan
>
> *
> * For searches and help try:
> * http://www.stata.com/help.cgi?search
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
