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Re: st: Cox Regression - flat region resulting in a missing likelihood


From   graupel75@gmail.com
To   Statalist <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Cox Regression - flat region resulting in a missing likelihood
Date   Tue, 30 Apr 2013 09:25:58 +0800

One other option is a convergence trick from 'Methods for estimating
adjusted risk ratios' by Peter Cummings, The Stata Journal (2009) 9,
Number 2, pp. 175–196.

http://www.stata-journal.com/sjpdf.html?articlenum=st0162

It's the last paragraph on pg 180.

On Tue, Apr 30, 2013 at 8:04 AM,  <graupel75@gmail.com> wrote:
> Theresa writes:
>
>> I set my data stset and then I tried to run a stcox and got the following
>> error message " flat region resulting in a missing likelihood r(430)";
>
> I would first try to change the settings for ties (Efron, exactp,
> exactm) if you have many tied failure times.
>
> Beyond that, it likely due to so-called 'mono-tone' likelihood;
> there's a solution called the Firth method. Unfortunately, it is not
> implemented in Stata for Cox models (but is in Some Alternative
> Software and in R).
>
> You could also try to randomize your times slightly (which likely
> won't work); use flexible parametric models which will require some
> startup (-ssc install stpm2-); or do a Poisson regression to get
> (essentially) the same coefficients as Incident Rate Ratios instead of
> HRs. Best source of how to do this is Dupont's 'Statistical Modeling
> for Biomedical Researchers'.
>
> cheers-
> Andrew Lover
> ______________________________________________
> Epidemiologist
> Centre for Infectious Disease Epidemiology Research (CIDER)
> Saw Swee Hock School of Public Health
> National University of Singapore

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