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Re: st: statsby slowness


From   "E. Paul Wileyto" <epw@mail.med.upenn.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: statsby slowness
Date   Tue, 14 Aug 2007 06:40:00 -0400

For large numbers of "by groups," I have found it works better/faster to write my own script that repeatedly pulls the original file from a tempfile, and then uses a keep statment to restrict the analysis. Statsby spends too much time looking to see who is in.

P

David Airey wrote:

.

At what point does one give up using statsby? With just three variables in my data set,

ssrownum, iso_VSV, expression

the following command does OK with 1000 by groups (< 20 cases in a group), but is not useable with 20,000 by groups.

statsby n=r(N) spearman=r(rho) p=r(p), by(ssrownum): spearman iso_VSV expression

Why?

I posted something similar a long time ago compared speeds of ttest with if versus in and versus regress, but I'm not happy at the moment.


--
David C. Airey, Ph.D.
Research Assistant Professor

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--
E. Paul Wileyto, Ph.D.
Assistant Professor of Biostatistics
Tobacco Use Research Center
School of Medicine, U. of Pennsylvania
3535 Market Street, Suite 4100
Philadelphia, PA 19104-3309

215-746-7147
Fax: 215-746-7140
epw@mail.med.upenn.edu
http://mail.med.upenn.edu/~epw/
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