Re: st: Change reference group in logistic regression

["Michael N. Mitchell" <Michael.Norman.Mitchell@gmail.com>]

Dear Morten

  If you are using Stata 11, you can get rid of the xi: prefix and specify the omitted 
group like this...

logit foreign ib3.rep78

  which says that -rep78- is an indicator variable, and the baseline (omitted) group is 
3. Or you can say

logit foreign ib4.rep78

  and the fourth group is the omitted group.

The -fvset- command can be used to permanently change the reference group (like the -char- 
command).

I hope that helps,

Michael N. Mitchell
Data Management Using Stata      - http://www.stata.com/bookstore/dmus.html
A Visual Guide to Stata Graphics - http://www.stata.com/bookstore/vgsg.html
Stata tidbit of the week         - http://www.MichaelNormanMitchell.com



On 2011-02-03 6.57 AM, Maarten buis wrote:
> --- On Thu, 3/2/11, Morten Stover wrote:
> > I want to change reference group doing a logistic
> > regression analysis on highest level of education and
> > future work disability. The data is coded 1=primary,
> > 2 =secondary and 3=tertiary, and I would like tertiary
> > to be the reference group. I've done this in cox
> > regression using char and [omit], but I can't get this
> > to work in log reg.
>
> I am assuming you are using the -xi- prefix. I cannot
> replicate your problem. The example below works as
> expected.
>
> *--------- begin example ----------
> sysuse auto, clear
> recode rep78 1/2=3
>
> char rep78[omit] 5
> xi: logit foreign i.rep78
> *----------- end example -----------
>
> Can you change the example above such that it reproduces
> your problem? Seeing the problem on your own computer in
> examples like that really help in diagnosing the problem.
>
> -- Maarten
>
> --------------------------
> Maarten L. Buis
> Institut fuer Soziologie
> Universitaet Tuebingen
> Wilhelmstrasse 36
> 72074 Tuebingen
> Germany
>
> http://www.maartenbuis.nl
> --------------------------
>
>
>
>
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