st: Pairing predictors in tuples.

[Bradley Fedy <fedyb@usgs.gov>]

Hi,

I am using tuples to cycle through models using different subsets of
predictors.  My code looks something like this:

tuples x1 x2 x3 x4 x5
forval i = 1/31{
      logit y `tuple`i"
}

However, I do not want all possible combinations.  I would like predictors
x4 and x5 to always enter the model together (i.e. one cannot be present
without the other).

Any suggestions on how to make x4 and x5 always enter the model together
would be greatly appreciated.

Thanks,
Brad

Stata Ver. 10.1


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