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st:A question related to mixlogit package

From   Nina YIN <>
Subject   st:A question related to mixlogit package
Date   Fri, 1 Jun 2012 10:11:01 +0200

Dear all,

I am currently using comand( mixlogit) to estimate mixed logit model
with individual-level data and have some questions to ask for your

I want to estimate the demand of prescription drug with data of
purchasing records, drug characteristics and individual demographics.

When I use the command,

-mixlogit choice price, group(ncs) id(np) rand(drug characteristics,
individual characteristics, interaction terms)

The results always return with" Variable education has no within-group
variance" or "Variable age has no within-group variance".

In my sample, there have some individual has repeated purchasing,
therefore, as a start, I excluded all the repeated records such that
for each individual there is only one purchasing record. However, it
also returned with this message. I can't get what does it mean. Does
that mean in this type of model, I couldn't include the individual
attribute variables except the interacted terms?

If you ever have had such experience, could you share me with your
opinion? Thanks a lot!

Best Regards,
Nina YIN

Toulouse School of Economics
Manufacture des Tabacs
21 Allee de Brienne
Toulouse, 31000, France
Tel: 0033-(0)5 6123 8348
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