Re: st: Conditional logistic regression: how to

[Marta Garcia-Granero <mgarciagranero@gmail.com>]

Ah! Now I see.

Shouldn't your final command be:

mi estimate: clogit _case x1 x2, group(_set)

HTH,
Marta

El 18/11/2013 10:11, Liliana Andriano escribió:
> Thank you for your reply Marta. The fact is that I need to estimate
> the fixed effects logit regressions relying on conditional logits,
> also known as the case-control technique (Chamberlain, 1980), so I
> should randomly select pairs from each
> sample, consisting of one death reported during five years preceding
> the survey and one birth that still survived at the survey time. For
> this I have realized that the sttocc command in Stata allows you to
> convert survival-time data to case-control data, but before running
> it, the declaration of survival data is necessary.
>
> Do you know if I randomly select pairs from each sample even though I
> am not declaring survival data and then converting survival-time data
> to case-control data?
>
> Your help is very appreciated.
> Many thanks in advance.
>
> Best,
> Liliana
>
>
>
> 2013/11/18 Marta Garcia-Granero <mgarciagranero@gmail.com>:
> > Hi Liliana:
> >
> > Maybe I am missing something, because I'm no Stata expert.
> >
> > As a former SPSS user, a program that did not have a specific command for
> > conditional logistic, I used the well known trick of using survival analysis
> > (Cox) instead. Since Stata has -clogit-, I don't think you need to declare
> > survival data before running it.
> >
> > See this simple example (maybe too simple) where -clogit- and -stcox-
> > outputs are exactly the same.
> >
> > * Sample data from www.hrc.es/bioest/Reglog_9.html (coding for hepat had to
> > be reversed!!) *
> > input hepat alcoh drug stratum
> > 1 15 1  1
> > 0 10 0  1
> > 0  0 0  1
> > 1 70 1  2
> > 0 20 0  2
> > 0 30 0  2
> > 1 40 1  3
> > 0 40 0  3
> > 0  0 0  3
> > 1 10 0  4
> > 0 20 1  4
> > 0 50 0  4
> > 1 30 1  5
> > 0 10 0  5
> > 0 20 0  5
> > 1 80 0  6
> > 0 20 0  6
> > 0 30 0  6
> > 1 50 1  7
> > 0 35 0  7
> > 0 10 0  7
> > 1 60 1  8
> > 0  5 0  8
> > 0 10 0  8
> > 1 90 0  9
> > 0 65 0  9
> > 0  5 0  9
> > 1 30 1 10
> > 0 10 0 10
> > 0 40 0 10
> > end
> >
> > * Using clogit *
> > clogit hepat c.alcoh i.drug c.alcoh#i.drug, group(stratum) or
> >
> > * using Cox *
> > gen ptime=1+(hepat==0)
> > stset ptime, failure(hepat==1)
> > stcox c.alcoh i.drug c.alcoh#i.drug, strata(stratum)
> >
> > I hope this helps
> >
> > Marta García-Granero, PhD
> > Dpt. of Biochemistry and Genetics,
> > University of Navarra
> >
> > El 14/11/2013 15:59, liliana escribió:
> >
> > > Dear statlist users,
> > >
> > > I am trying to run a conditional logistic regression. The analysis
> > > consists
> > > of studying the determinants of child mortality. Before running the
> > > conditional logistic regression I should randomly select pairs from each
> > > sample, consisting of one death reported during five years preceding the
> > > survey and one birth that still survived at the survey time. Moreover, I
> > > have also imputed the missing values of an explanatory variables, which
> > > means that before the stata command I should insert the mi estimate:
> > > option.
> > >
> > > What I have done in Stata is
> > >
> > > set seed 8021
> > >
> > > then I have declared my data to be survival data and then
> > >
> > > sttocc, match(mortality), where mortality is a dummy variable assuming
> > > value
> > > 0 if the child died during five years preceding the survey.
> > >
> > > Then I go with:
> > >
> > > mi estimate: clogit y x1 x2, group(_set)
> > >
> > > Stata tells me that
> > >
> > > (regular variables _st _d _t _t0 unregistered because not in m=0)
> > > groups (strata) are not nested within clusters
> > > an error occurred when mi estimate executed clogit on m=1
> > > r(459);
> > >
> > >
> > > May you tell me what's wrong with these commands, please?
> > >
> > > Thank you very much.
> > >
> > > Best,
> > > Liliana
> > >
> > >
> > >
> > >
> > > --
> > > View this message in context:
> > > http://statalist.1588530.n2.nabble.com/Conditional-logistic-regression-how-to-tp7580452.html
> > > Sent from the Statalist mailing list archive at Nabble.com.
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