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
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