[Limdep Nlogit List] Problem with NLSUR

[William Greene]

Mr. Rao.
(1) The warning about the log likelihood is harmless if the derivatives
are small and you have made more than a few iterations. In your case,
it sounds like it can be ignored.
(2) NLSUR iterates over the covariance matrix outside the iterations 
for the parameters. Each time it "jumps back" it is updating the 
disturbance covariance matrix and reentering the iterations.
B. Greene

----- Original Message -----
From: "James Rao" <James.Rao at agr.uni-goettingen.de>
To: "Limdep and Nlogit Mailing List" <limdep at limdep.itls.usyd.edu.au>
Sent: Friday, May 15, 2009 12:32:19 PM GMT -05:00 Columbia
Subject: Re: [Limdep Nlogit List] Problem with NLSUR


Hi,

Back to my usual problem with NLSUR ...... my iterations converged well, but
there are two or three lines of error messages saying that "The log
likelihood is flat at current estimates". What could be the implications of
this error? Does it mean that the iterations did not actually converge? And
what could be a potential solution to this problem?

The second concern is that the iterations proceed smoothly but then jump back
to first iteration after some iterations .... say 15 iterations. What could
be the cause of these jumps?

Sincerely
=============================================================================
==
Rao E.O. James (Msc)
Research Associate/PhD Student

Department of Agricultural Economics and Rural Development
Georg-August University of Göttingen
Platz der Gottinger Sieben 5
37073 Göttingen, Germany.
 
Tell:+49-551-394443 (Office)
E-mail: jimrao2 at yahoo.co.uk;  James.Rao at agr.uni-goettingen.de

Courage is not the absence of fear but the triumph over it ... so fear not to
fear ... but strive to overcome fear!




-----Original Message-----
From: limdep-bounces at limdep.itls.usyd.edu.au on behalf of Rao, James
Sent: Tue 4/28/2009 5:27 PM
To: Limdep and Nlogit Mailing List
Subject: Re: [Limdep Nlogit List] Problem with NLSUR
 
Hi, 

In estimating the a non linear systems of equations am using the NLSUR
command that corresponds to "nonlinear IV systems of equations (NL3SLS)". In
the table of results shown below, I wonder whether or not its right that the
"Number of parameters is shown to be = 0"

Is it also right that my information criteria are all the same?

+---------------------------------------------+
| Nonlinear minimization over  3 equations.   |
| Maximum Likelihood Estimates                |
| Model estimated: Apr 24, 2009 at 03:17:54PM.|
| Dependent variable             MultEqns     |
| Weighting variable                 None     |
| Number of observations              402     |
| Iterations completed                 17     |
| Log likelihood function        101.8690     |
| Number of parameters                  0     |
| Info. Criterion: AIC =          -.50681     |
|   Finite Sample: AIC =          -.50681     |
| Info. Criterion: BIC =          -.50681     |
| Info. Criterion:HQIC =          -.50681     |
| Disturbances are   correlated               |
| Covariance matrix used is (1/N)E'E          |
| Number of iterations over S is    11        |
| Used multiple    equation nonlinear 3S-IV.  |
| McElroy R-squared for the system =  .46612  |
+---------------------------------------------+


=============================================================================
==
Rao E.O. James (Msc)
Research Associate/PhD Student

Department of Agricultural Economics and Rural Development
Georg-August University of Göttingen
Platz der Gottinger Sieben 5
37073 Göttingen, Germany.
 
Tell:+49-551-394443 (Office)
E-mail: jimrao2 at yahoo.co.uk;  James.Rao at agr.uni-goettingen.de

Courage is not the absence of fear but the triumph over it ... so fear not to
fear ... but strive to overcome fear!


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