Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
From | graupel75@gmail.com |
To | Statalist <statalist@hsphsun2.harvard.edu> |
Subject | st: Cox Regression - flat region resulting in a missing likelihood |
Date | Tue, 30 Apr 2013 08:04:44 +0800 |
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 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/