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Re: st: FIRTHLOGIT with factor (categorical variables)
From
Maarten buis <[email protected]>
To
[email protected]
Subject
Re: st: FIRTHLOGIT with factor (categorical variables)
Date
Tue, 21 Sep 2010 14:03:15 +0000 (GMT)
--- On Tue, 21/9/10, Warren Chow wrote:
> But the following does not work:
>
> firthlogit y i.x
>
> Is there another version of the macro that supports factor
> variables, or an easy way to modify to code? I have tried
> the following:
>
> xi : firthlogit y i.x
> But this is extremely slow.
That is the right solution, so if you want to use -firthlogit
you'll just have to learn to live with the slowness. Moreover,
I am always left with a feeling of arbitrariness when it
comes to the kind of penelized likehood used in -firthlogit-.
I guess it won't matter too much in most practical application,
but the logic doesn't sound too convincing to me (or I just do
not understand it...).
You could try -exlogistic- but i doubt whether that is going to
be quicker. Do not be fooled by the name though: exact methods,
like -exlogistic-, sound great, but they are not as exact as the
name suggest. On many properties that we care about, like
coverage, the "exact" methods under perform compared to
"non-exact" methods.
Alternatively, you can try to combine some categories of x1, so
you can just use -logit-. As always, I prefer to simplify the
model in cases like these, so that would be my prefered approach.
Hope this helps,
Maarten
--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany
http://www.maartenbuis.nl
--------------------------
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