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st: Thread-Index: Ac2zpwBrnny9GG5FQQ6Vz7stZfQOCw==


From   Amal Khanolkar <Amal.Khanolkar@ki.se>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: Thread-Index: Ac2zpwBrnny9GG5FQQ6Vz7stZfQOCw==
Date   Fri, 26 Oct 2012 18:25:48 +0000

Hi,

I tried running the lroc command following my logistic regression as follows:

xi: logistic moth_wtgain_under i.mom_race2 age_mom sexx if parity!=. & gestwk_cat!=. & cigs_befx!=. & cigs_1stx!=. & cigs_2ndx!=. & cigs_3rdx!=. & gestdb!=. & gesthy!=. & ht_cm!=. & plural==1 & edu_mom!=. & marriedxx!=.
lroc, nograph
predict xb1 xb

Based on an example I saw online in the Stata manual, I use 'predict' as above to produce a linear predictor model. I do the same for another 4 models, i.e.

logistic model 2
lroc, nograph 
predict xb2 xb

logistic model 3
lroc, nograph 
predict xb3 xb

..... and so on. 

All four logistic models have the same outcomes, but different explanatory variables. My aim is use the roccomp command as follows to be able to compare all 4 models easily:

roccomp hon xb1 xb2 xb3 xb4, graph summary


1. I get an error message after running the first 'predict xb1 xb' above.  ('too many variable specified'). I didn't think this would be a problem. Is there any way I can get around this, or do I have to r educe the number of covariates specified in my logistic model?

2. Or is there a better approach?

Thanks!

/Amal.









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