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re: Re: st: RE: problem with factor variable and margins.


From   Christopher Baum <baum@bc.edu>
To   statalist@hsphsun2.harvard.edu
Subject   re: Re: st: RE: problem with factor variable and margins.
Date   Wed, 17 Mar 2010 13:35:08 -0400

<>
Rich said

I think I have tracked down the problem.  In addition to the factor 
variable nainc, I have a continuous variable nainc_ainc as a regressor 
(which is the indicator times a continuous variable).  The margins 
command then got confused and assumed that nainc was an abbreviation for 
nainc_ainc, which did appear in the results and subsequent tests.  When 
I rename nainc_ainc as n2ainc_ainc, my problem goes away -- a marginal 
effect for the discrete change in the factor variable nainc does indeed 
show up in the results.

If I am right in diagnosing why the rename solves the problem, this 
means there is a bug in stata's margins.  It is not reporting an 
ambiguous abbreviation, it is simply picking one.  Should I report it to 
stata's tech staff, or is that something you do, Martin?


Although there may indeed be a need for revision of -margins- code, I am curious if you would get this
same error if you did 

set varabbrev, off


I would recommend

set varabbrev off, permanent

Kit Baum   |   Boston College Economics and DIW Berlin   |   http://ideas.repec.org/e/pba1.html
An Introduction to Stata Programming   |   http://www.stata-press.com/books/isp.html
An Introduction to Modern Econometrics Using Stata   |   http://www.stata-press.com/books/imeus.html


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