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Re: st: Collecting Statistics of Averages of Variables


From   robert hartman <rohartman@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Collecting Statistics of Averages of Variables
Date   Sat, 29 Sep 2012 17:35:52 -0400

By my lights, the number of unique combinations of 2 variables from a
pool of 70 variables is 2415. That's a lot but not intractable

On Sat, Sep 29, 2012 at 12:39 PM, Clyde B Schechter
<clyde.schechter@einstein.yu.edu> wrote:
> 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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