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Re: st: Factor variable notation vs. hand made dummy vars
From
[email protected] (Brendan Halpin)
To
[email protected]
Subject
Re: st: Factor variable notation vs. hand made dummy vars
Date
Mon, 06 Feb 2012 15:41:52 +0000
To put the "why" back one step, the immediate reason is evident from the
output
| . logit for mpg d2-d5
|
| note: d2 != 0 predicts failure perfectly
| d2 dropped and 8 obs not used
|
| [...]
|
| . logit for mpg ib1.rep78
|
| note: 1.rep78 != 0 predicts failure perfectly
| 1.rep78 dropped and 2 obs not used
|
| note: 2.rep78 != 0 predicts failure perfectly
| 2.rep78 dropped and 8 obs not used
|
| note: 5.rep78 omitted because of collinearity
|
| [...]
You end up fitting different models on different data.
The question is now why do the formulations behave differently, and
which is the better default?
Brendan
--
Brendan Halpin, Department of Sociology, University of Limerick, Ireland
Tel: w +353-61-213147 f +353-61-202569 h +353-61-338562; Room F1-009 x 3147
mailto:[email protected] ULSociology on Facebook: http://on.fb.me/fjIK9t
http://teaching.sociology.ul.ie/bhalpin/wordpress twitter:@ULSociology
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