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Re: st:A question related to mixlogit package


From   Nina YIN <yinnina.ccer@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st:A question related to mixlogit package
Date   Tue, 5 Jun 2012 17:48:44 +0200

Hi Arne,

Thanks a lot for your suggestions! Now I got what it means.

On Fri, Jun 1, 2012 at 10:58 AM, Arne Risa Hole <arnehole@gmail.com> wrote:
> Nina
>
> The message means what it says; variables must vary over
> groups/alternatives to be included in the model. This is also true for
> the standard conditional logit which can be estimated with -clogit-
> and/or -asclogit-. You should always start with these models first
> before trying to run a mixed logit – if you can't get -clogit- to run
> you can be 100% sure that -mixlogit- won’t either so this is a good
> way to discover fundamental problems with your model spec.
>
> Arne
>
> On 1 June 2012 09:11, Nina YIN <yinnina.ccer@gmail.com> wrote:
>> 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
>> help.
>>
>> 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
>> *
>> *   For searches and help try:
>> *   http://www.stata.com/help.cgi?search
>> *   http://www.stata.com/support/statalist/faq
>> *   http://www.ats.ucla.edu/stat/stata/
>
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/



-- 
Best Regards,
Nina YIN


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

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/


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