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R: st: convergence problem


From   "Carlo Lazzaro" <carlo.lazzaro@tin.it>
To   <statalist@hsphsun2.harvard.edu>
Subject   R: st: convergence problem
Date   Tue, 11 Sep 2007 17:30:27 +0200

Dear Maarten,

thanks a lot for your kind reply. I have shifted to the AIC informative
criteria to check for the appropriateness and I found out the Gompertz model
seems to fit to my data.

Thanks a lot again and kind regards,

Carlo
-----Messaggio originale-----
Da: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di Maarten buis
Inviato: marted́ 11 settembre 2007 16.32
A: statalist@hsphsun2.harvard.edu
Oggetto: Re: st: convergence problem

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 <carlo.lazzaro@tin.it> 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
> 
> 
> *
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> 


-----------------------------------------
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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