st: Storing coefficients from a stepwise model

[Elaine Thomas <e.thomas@cphc.keele.ac.uk>]

Dear all

I want to perform a stepwise logistic procedure on a number of 
bootstrapped samples and store the coefficients from each application of 
the regression in a single file.
I have thus far been able to generate the bootstrapped samples (thanks 
to David Harrison!) and store the coefficients - however, only if I do 
not use a stepwise approach to the regression, but simply tell it to fit 
a model containing a set number of independent variables, say x1 -x5, - 
this works well. So I get a single new file which contains the 
coefficients for each cycle, ie

Sample         x1        x2        x3        x4        x5
  1             0.24    0.35     0.84    0.08     0.75
  2             0.22    0.40     0.78    0.12     0.69 ......

The complication in using the sw procedure is that the model derived in 
each sample may contain anywhere from all to none of the variables 
offered and when I try to get Stata to store the coefficients for the 
offered vbls, say x1-x5, I can't get it to store "." for those vbls that 
are not chosen in that cycle of the procedure

What I want is the same form of file as above but with . or even 0 for 
those vbls not ending up in the model for that sample, ie.

Sample         x1        x2        x3        x4        x5
  1             0.24        0      0.84    0.08     0.75
  2             0.22    0.40     0.78        0      0.69 ......

Any help would be gratefully received

Best wishes
Elaine Thomas


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