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From |
"Glenn Goldsmith" <glenn.goldsmith@gmail.com> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: Matrix transformation |

Date |
Sat, 4 Apr 2009 00:08:03 +0100 |

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" <olivia@primal.ucdavis.edu> 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/

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