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Re: st: Factor variable notation vs. hand made dummy vars
From
Richard Williams <[email protected]>
To
[email protected], "[email protected]" <[email protected]>
Subject
Re: st: Factor variable notation vs. hand made dummy vars
Date
Mon, 06 Feb 2012 10:43:19 -0500
At 10:25 AM 2/6/2012, Ulrich Kohler wrote:
Hi all,
I cannot replicate the model
. sysuse auto, clear
. tab rep78, gen(d)
. logit for mpg d2-d5
with factor variable notation. I tried
. logit for mpg ib1.rep78
but results differ. Can anybody explain why?
(Note as an aside that
. logit for mpg d1-d5
reproduces the factor variables solution, but normally I would not
specify the model this way)
Two additional cases get dropped using factor variable notation. I'm
guessing that with the first approach, Stata is having trouble
distinguishing perfect multicollinearity from extreme
multicollionearity. rep78 has some very small Ns for some of its
categories, which is one of the reasons I don't like to use it in any
examples I do.
-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
HOME: (574)289-5227
EMAIL: [email protected]
WWW: http://www.nd.edu/~rwilliam
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