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| From | Clyde B Schechter <clyde.schechter@einstein.yu.edu> |
| To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
| Subject | Re: st: Collecting Statistics of Averages of Variables |
| Date | Sat, 29 Sep 2012 16:39:23 +0000 |
Robert Hartman asked about calculating summary statistics from all possible combinations of some variables. The example in his initial post involved 4 variables, which should be no problem at all. But at the end of his post he says: "I have about a 70 variable space from which to create all these subset combinations." If that means that he wants to do this for all possible combinations of 70 variables, that is 2^70 (= 1.181e+21) combinations to work out. That's beyond merely time consuming: if each combination can be completely processed in 1 microsecond, we are looking at over 37,000,000 years of processing. It's examples like this that evoke the phrase "combinatorial explosion." Perhaps the whole approach needs to be reconsidered. Clyde Schechter Dept. of Family & Social Medicine Albert Einstein College of Medicine Bronx, NY, USA * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/