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

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

Subject |
Re: Re: st: Making a Matrix from Three Variables |

Date |
Sun, 10 May 2009 11:45:01 +0100 |

<> Good call on the missing values front. The other thing to potentially be wary of is that missing values in your rows or cols variables will cause the -sparse()- code to do odd things. A possible fix is below, but it may be easiest just to ensure there aren't any missing values in your initial x matrix. ********************************************************* mata: real matrix sparse(real matrix x) { real matrix y real scalar k y = J(colmax(x[,1]),colmax(x[,2]),.) for (k=1; k<=rows(x); k++) { if (x[k,1]!=. & x[k,2]!=.) y[x[k,1],x[k,2]] = x[k,3] } return(y) } end ********************************************************** Tirthankar Chakravarty <tirthankar.chakravarty@gmail.com> wrote: <> <> Many apologies. Read Glenn for Allan. T On Sat, May 9, 2009 at 10:38 PM, Tirthankar Chakravarty <tirthankar.chakravarty@gmail.com> wrote: > <> > <> > 1) Amadou's solution can be streamlined considerably by replacing the > first part as in the code included below. > > 2) The line: > tomata x y z, missing > does not work because -missing- is not a valid option for -tomata- (Gould, SSC). > > 3) Allan's solution is efficient, but you might want to watch out for > missing values in your original data. So, a slight modification is > included below. * * 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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