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Re: st: NLOGIT


From   "Rodrigo A. Alfaro" <raalfaroa@gmail.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: NLOGIT
Date   Thu, 26 Jul 2007 00:10:57 -0400

Check that

(1) Your Stata is updated. -nlogit- was fixed for missing observations.
(2) Your covariates are not all dummies. Manos suggested to get
some multiplicative variables: something like "married (dummy) times
income (in dollars)". Also, if ageskl is age times dummy-skilled and
age times dummy-unskilled why you have both?
(3) Drop the nolog in the process... maybe there is some information
that we/you want to know, such as "not concave", "variable xyz
dropped due to collinearity", etc.
(4) Run a SIMPLE version of the model... I meant really simple.
You should play with fraction of your dataset, and less covariates.

Rodrigo.


----- Original Message ----- From: "Neil Shephard" <nshephard@gmail.com>
To: <statalist@hsphsun2.harvard.edu>
Sent: Tuesday, July 24, 2007 8:13 AM
Subject: Re: st: NLOGIT



MNL == Multiple Nested Logit?

You've given us the command that you use, but not shown what the
error's Stata is reporting are. These are likely to be informative in
helping resolve your problem.

From the FAQ (http://www.stata.com/support/faqs/res/statalist.html#advice)...

* Say exactly what you typed and exactly what Stata typed (or did)
in response. N.B. exactly! If you can, reproduce the error with one of
Stata's provided datasets or a simple concocted dataset that you
include in your posting.

Don't send examples like this, which gives no information:
o The command -fiddle- worked yesterday, but it is not working today.

or like this, which gives very little information:

* I am using -frog-, but I just get the message "invalid syntax".

This example shows better style, setting aside the fact that its
answer can be found in the online help:

* I am using Stata 9 to try to draw a plot using -scatter-.
Here is an example showing my problem with the auto data:

. scatter mpg weight, s(p)

I get lots of very small points. Why doesn't Stata use plus symbols?

Neil

On 7/24/07, Bidisha Sayema <lexshb@nottingham.ac.uk> wrote:

Dear Statalisters,

I have done a MNL of employment status (4 choices: wage employed,
unemployed etc) with individual specific controls eg sex, education,
age, race etc and in the next stage with only the wage employed run
another MNL of occupational choices (3 choices: skilled, unskilled etc)
with controls like the first stage (not the same though). But I also
want to do a NLOGIT while incorporating all the decisions, so there will
be 6 choices in the bottom set (3 choices out of wage employed, 3
remaining categories of employment status) along with the first set of 4
alternatives. I constructed the data set and the tree is running fine
but I was unable to run NLOGIT and was facing error message. Is it due
to the use of common individual specific variables in both stages? But I
need to have demographic and education variables in both stages. Any
suggestion is highly appreciated. A simple version of the model is as
follows:

nlogit choice (occchoice=ageprof ageskl ageuskl agesemp ageunemp agenemp
/*
*/ age2prof age2skl age2uskl age2semp age2unemp age2nemp)
(empstat=ageemp2 ageemp3 ageemp4 /*
*/ age2emp2 age2emp3 age2emp4 marriedemp2 marriedemp3 marriedemp4),
group(caseno) nolog

Best Regards
Bidisha


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them." - Johann von Neumann

Email - nshephard@gmail.com / n.shephard@sheffield.ac.uk
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