Re: st: Conditional logistic regression: how to

[Liliana Andriano <liliana.andriano@gmail.com>]

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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>>
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