[Limdep Nlogit List] random parameters logit

[Marjolein Maria Juliette Harmsen-van Hout]

Dear prof. Greene,

Thanks for your reply. Even estimation with 500 Halton draws provides the same difference. Moreover, the program claims normal exit for both models: 

1st model: "* Converged Normal exit from iterations. Exit status=0. Function=  .11994470974D+04, at entry,  .11904739292D+04 at exit Error  1027: Models - estimated variance matrix of estimates is singular"

2nd model: "* Converged Normal exit from iterations. Exit status=0. Function=  .11906631459D+04, at entry,  .11817440931D+04 at exit +---------------------------------------------+ | Random Parameters Logit Model etcetera"

In case of either of your suggested possibilities, in how far can I trust the estimations found with my 2nd model?

Best regards,
Marjolein Harmsen - van Hout


On 17/09/10, William Greene  <wgreene at stern.nyu.edu> wrote:

> Dear Marjolein. It does appear that the two commands should produce
> the same model and, using Halton draws, the same results.  
> I can see two possibilities:
> (1) Although the models are the same, the starting values for the
> mixed logit estimates are not the same in the two cases. In the first
> case, the starting value for the interaction term would be zero. In 
> the second, it would be the MNL coefficient.  It is possible that the
> mixed logit has the kind of ill behaved log likelihood that would 
> produce this result.  
> (2) A less likely possibility is that rounding error in the computations 
> in the first case is producing the problem. This would imply that the 
> data set is very badly conditioned.
> Theory (1) sound more likely to me.  The second set of results are
> obviously to be preferred. I would add ;OUTPUT=3 to your command to
> display the derivatives during the solution, and verify that you really
> did get a normal exit from the optimizer with the second specification.
> I would also suggest increasing the number of draws to, say, 100. This 
> may help.
> /Bill Greene
> 
> ----- Original Message -----
> From: "Marjolein Maria Juliette Harmsen-van Hout" <Marjolein.harmsen at rwth-aachen.de>
> To: limdep at limdep.itls.usyd.edu.au
> Sent: Friday, September 17, 2010 4:24:05 AM GMT -05:00 Colombia
> Subject: Re: [Limdep Nlogit List] random parameters logit
> 
> 
> Dear all,
> As I did not receive any reply to my previous message, I hereby send it once more. If you need more information, please notify me. Thanks!
> 
> On 25/08/10, "Marjolein Maria Juliette Harmsen-van Hout"  <Marjolein.harmsen at rwth-aachen.de> wrote:
> 
> > > Dear all,
> > > 
> > > I encountered the following puzzle with my dataset:
> > > 
> > >  NLOGIT;
> > >  Lhs=CHOICE,CSET,ALT;
> > >  Rhs=VAR1;
> > >  Pds=PER;
> > >  Rpl=VAR2;
> > >  Fcn=VAR1(N);
> > >  Halton;Pts=20$	
> > > 
> > > leads to Error 1027: Models - estimated variance matrix of estimates is singular, whereas:
> > > 
> > >  CREA;VAR1_VAR2=VAR1*VAR2$
> > >  NLOGIT;
> > >  Lhs=CHOICE,CSET,ALT;
> > >  Rhs=VAR1,VAR1_VAR2;
> > >  Pds=PER;
> > >  Rpl;
> > >  Fcn=VAR1(N);
> > >  Halton;Pts=20$        	
> > > 
> > > provides normal estimations. Does anybody have an idea how this could be possible?
> > > 
> > > Thanks in advance for your reaction!
> > > 
> > > Kind regards, 
> > > ____________________________________________________________
> > > 
> > > Dr. drs. Marjolein Harmsen - van Hout
> > > Post-doctoral researcher
> > > 
> > > Tel.: +49 241 80 49835
> > > Fax: +49 241 80 49829
> > > E-mail: mharmsen at eonerc.rwth-aachen.de
> > > Website: www.eonerc.rwth-aachen.de
> > > 
> > > Lehrstuhl für Wirtschaftswissenschaften, insb. Energieökonomik
> > > Institute for Future Energy Consumer Needs and Behavior (FCN)
> > > E.ON Energy Research Center (E.ON ERC)
> > > RWTH Aachen University
> > > Mathieustraße 6, D-52074 Aachen
> > > Germany
> > > ____________________________________________________________
> -- 
> ____________________________________________________________
> 
> Dr. drs. Marjolein Harmsen - van Hout
> Post-doctoral researcher
> 
> Tel.: +49 241 80 49835
> Fax: +49 241 80 49829
> E-mail: mharmsen at eonerc.rwth-aachen.de
> Website: www.eonerc.rwth-aachen.de
> 
> Lehrstuhl für Wirtschaftswissenschaften, insb. Energieökonomik
> Institute for Future Energy Consumer Needs and Behavior (FCN)
> E.ON Energy Research Center (E.ON ERC)
> RWTH Aachen University
> Mathieustraße 6, D-52074 Aachen
> Germany
> ____________________________________________________________
> _______________________________________________
> Limdep site list
> Limdep at limdep.itls.usyd.edu.au
> http://limdep.itls.usyd.edu.au
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-- 
____________________________________________________________

Dr. drs. Marjolein Harmsen - van Hout
Post-doctoral researcher

Tel.: +49 241 80 49835
Fax: +49 241 80 49829
E-mail: mharmsen at eonerc.rwth-aachen.de
Website: www.eonerc.rwth-aachen.de

Lehrstuhl für Wirtschaftswissenschaften, insb. Energieökonomik
Institute for Future Energy Consumer Needs and Behavior (FCN)
E.ON Energy Research Center (E.ON ERC)
RWTH Aachen University
Mathieustraße 6, D-52074 Aachen
Germany
____________________________________________________________