A simple but not very satisfactory answer is that if the model does not
converge it is probably not appropriate...
Hope this helps,
Maarten
--- Carlo Lazzaro <[email protected]> wrote:
> Dear Statalisters,
>
> fittine a generalized gamma model with Stata 9.2/SE for testing via
> K=1 test
> the appropriateness of the Weibull parametric survival model, I get
> the
> following lines and error (not convergence).
>
>
> . streg DMD, dist(gamma) technique(nr)
>
> failure _d: MS_Conv == 1
> analysis time _t: risk_time
> id: id
>
> Fitting constant-only model:
>
> Iteration 0: log likelihood = -218277.41 (not concave)
> Iteration 1: log likelihood = -176430.05
> Iteration 2: log likelihood = -154374.58 (not concave)
> Iteration 3: log likelihood = -129998.81
> Iteration 4: log likelihood = -109341.76 (not concave)
> Iteration 5: log likelihood = -98110.045
> Iteration 6: log likelihood = -90070.512
> Iteration 7: log likelihood = -85689.478
> Iteration 8: log likelihood = -84370.382
> discontinuous region encountered
> cannot compute an improvement
> r(430);
>
> Is there any other way for working this problem around and checking
> for the
> appropriateness of Weibull model?
>
> Thanks a lot for your kindness and for your time.
>
> Kind Regards,
>
> Carlo
>
>
> *
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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