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Re: st: Collecting Statistics of Averages of Variables

From   Clyde B Schechter <>
To   "" <>
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

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