Re: st: example about choice experiment datasheet

[Arne Risa Hole <arnehole@gmail.com>]

Elisabetta,

The "case" variable must a unique identifier for each choice. You can
generate it like this

egen caseid = group(id scenario)

The "alt" variable should be coded 1,2,3,4,1,2,3,4 etc. (not
1,2,3,4,5,6,7,8,...).

Arne

On 24 November 2012 16:04, elisabetta capobianco
<elisabetta.capobianco@gmail.com> wrote:
> Thank you Arne, I have taken the book.
> My problem is that I have 16 scenarios for id (n=131) with 4 different
> alternatives for each scenario .
> So in the dataset I have written for each id non 4 alternatives
> (1,2,3,4) but 64 alternatives. Is it correct?
>
>
>
> id   scenario      alt
> 1         1            1
> 1         1            2
> 1         1             3
> 1         1            4
> 1         2            5(or1?)
> 1         2            6(or2?)
> 1         2            7(or3?)
> 1         2            8 (or4?)
> 1         3            9(or1?)
> .
> .
> .
> .
> .
> 1         16           64
> 2         1              1
> .
> .
> And when I wrote:
> asclogit choice organic price, case(id) alternatives(car) noconst
>
> case is id or scenario? I suppose scenario. But if is scenario I don't
> know how to use id!
> And alternatives are the 64 alternatives?
>
>
> Thank you so much for your help.
>
> elisabetta
>
>
>
>
>
> 2012/11/23 Arne Risa Hole <arnehole@gmail.com>:
>> Elisabetta
>>
>> I am fairly sure that you can use -asclogit- to do what you want. If
>> you don't want alternative-specific constants you can use the
>> -noconst- option. Modifying the example in the help-file slightly:
>>
>> webuse choice
>> asclogit choice dealer, case(id) alternatives(car) noconst
>>
>> As you can see the only coefficient which is estimated in this case is
>> the one for the dealer attribute, which is analogous to the organic
>> and price attributes in your experiment. In your case the variable
>> that identifies the alternatives for each case ("car" in the example)
>> can simply take the values 1, 2, 3 and 4 since your alternatives are
>> unlabelled.
>>
>> I also recommend taking a look at a basic choice modelling text before
>> proceeding, such as
>> http://books.google.co.uk/books/about/Applied_Choice_Analysis.html?id=8yZrtCCABAgC.
>>
>> Good luck!
>>
>> Arne
>>
>> On 23 November 2012 13:25, elisabetta capobianco
>> <elisabetta.capobianco@gmail.com> wrote:
>>> I think that asclogit is not the right comand for me.
>>> Because I have 4 unlabeled alternatives, 16 diferrent scenarios with 4
>>> alternatives for 131 individuals. So my indipendent viariables are the
>>> attributes and dipendent variables the utility for each level of
>>> attribute.
>>> I need to know the importance of every level, not of alternatives.
>>> Ex.:n=131
>>> scenario 1)   A       B        C         D
>>>      organic  org   no org   no org   org
>>>      price       4         8         4         4
>>> scenario 2)   A      B         C        D
>>>     organic  no org  no org   org     no org
>>>       price     12     16         8        8
>>> .
>>> .
>>> .
>>> Perhaps with mixlogit? Because the example is on a specific
>>> alternative, car or bus.
>>> I instead need to know the coefficient of attributes and levels.
>>>
>>> I don't know if I have explained well, I hope!
>>>
>>> e
>>>
>>>
>>>
>>> 2012/11/23 Arne Risa Hole <arnehole@gmail.com>:
>>>> -help asclogit_postestimation-
>>>>
>>>> Arne
>>>>
>>>> On 23 November 2012 11:05, elisabetta capobianco
>>>> <elisabetta.capobianco@gmail.com> wrote:
>>>>> Dear Arne,
>>>>> i need to estimate the marginal effect of levels on attributes of my choice.
>>>>> Is it possible?
>>>>> es:
>>>>> about meat:
>>>>> attribute   level
>>>>> label        organic/not organic
>>>>> origin       local abroad
>>>>> prize        4/8
>>>>>
>>>>> I would know the utility for each level of each attribute.
>>>>>
>>>>> Thank you!
>>>>> elisabetta
>>>>>
>>>>>
>>>>>
>>>>> 2012/11/21 elisabetta capobianco <elisabetta.capobianco@gmail.com>:
>>>>>> Thank you so much Arne!!!
>>>>>> I'm creating the data set and then i'll try to run in Stata!
>>>>>>
>>>>>> Elisabetta
>>>>>>
>>>>>> 2012/11/20 Arne Risa Hole <arnehole@gmail.com>:
>>>>>>> Elisabetta
>>>>>>>
>>>>>>> -mlogit- is not very useful to model data from choice experiments as
>>>>>>> it does not allow alternative-specific explanatory variables.
>>>>>>> -asclogit- requires your data to be in long form (one row per
>>>>>>> alternative); see -help asclogit- and the first example in the paper I
>>>>>>> mentioned in my last email.
>>>>>>>
>>>>>>> Arne
>>>>>>>
>>>>>>> On 20 November 2012 10:04, elisabetta capobianco
>>>>>>> <elisabetta.capobianco@gmail.com> wrote:
>>>>>>>> Thank you Arne, I want to use asclogit and mlogit for my choice modelling.
>>>>>>>>
>>>>>>>>
>>>>>>>> 2012/11/19 Arne Risa Hole <arnehole@gmail.com>:
>>>>>>>>> Elisabetta
>>>>>>>>>
>>>>>>>>> As Jay says the correct data form depends on the estimation command
>>>>>>>>> you are planning to use, so this is a very important piece of
>>>>>>>>> information that you haven't given us. You may find the examples in
>>>>>>>>> http://www.stata-journal.com/article.html?article=st0133 useful.
>>>>>>>>> Generally speaking the best strategy is to import the data into Stata
>>>>>>>>> and then use commands like -reshape- to convert the data into the form
>>>>>>>>> you want, rather than trying to do this in Excel.
>>>>>>>>>
>>>>>>>>> Arne
>>>>>>>>>
>>>>>>>>>> On 19 November 2012 15:51, elisabetta capobianco
>>>>>>>>>> <elisabetta.capobianco@gmail.com> wrote:
>>>>>>>>>>>
>>>>>>>>>>> Thank you for your answer!
>>>>>>>>>>> I want to do a mixed logit, but I have found a data set on help file
>>>>>>>>>>> with just one choice set. I have 16 choice sets and I don't know how
>>>>>>>>>>> to fil the excel data set.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> 2012/11/18 JVerkuilen (Gmail) <jvverkuilen@gmail.com>:
>>>>>>>>>>> > On Sun, Nov 18, 2012 at 4:11 AM, elisabetta capobianco
>>>>>>>>>>> > <elisabetta.capobianco@gmail.com> wrote:
>>>>>>>>>>> >> Hi, I'm new of statalist and stata!
>>>>>>>>>>> >> I'm working on choice experiment about food preferences in schools.
>>>>>>>>>>> >> I have 4 alternatives unlabelled, 4 attributes and 4 levels, 130
>>>>>>>>>>> >> individuals.
>>>>>>>>>>> >> I have the data base in excel, but before insheet the file in stata
>>>>>>>>>>> >> i'm not sure that i have put the data in the right mode in the excel
>>>>>>>>>>> >> file.
>>>>>>>>>>> >> Have you got an example on a excel datasheet about choice modelling?
>>>>>>>>>>> >> Just an example to understand how to organize my datasheet.
>>>>>>>>>>> >
>>>>>>>>>>> > It depends on what analysis you want to use. -clogit- and procedures
>>>>>>>>>>> > like it that are using alternative-specific predictors use the same
>>>>>>>>>>> > basic format, which is specified in the help file. You can see the
>>>>>>>>>>> > example dataset there. Essentially it is a "long" format like
>>>>>>>>>>> > person-period in a growth model with time-varying covariates.
>>>>>>>>>>> > *
>>>>>>>>>>> > *   For searches and help try:
>>>>>>>>>>> > *   http://www.stata.com/help.cgi?search
>>>>>>>>>>> > *   http://www.stata.com/support/faqs/resources/statalist-faq/
>>>>>>>>>>> > *   http://www.ats.ucla.edu/stat/stata/
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
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>>>>>>>>
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>>>>>>>>
>>>>>>>>
>>>>>>>>           Le informazioni contenute in questa comunicazione e gli
>>>>>>>> eventuali documenti allegati
>>>>>>>>
>>>>>>>>           hanno carattere confidenziale e sono a uso esclusivo del
>>>>>>>> destinatario. Nel caso
>>>>>>>>
>>>>>>>>           questa comunicazione Vi sia pervenuta per errore, Vi informo
>>>>>>>> che la sua diffusione
>>>>>>>>
>>>>>>>>           e riproduzione è contraria alla legge e prego di darmi
>>>>>>>> prontamente avviso
>>>>>>>>
>>>>>>>>           e di cancellare quanto ricevuto. Grazie.
>>>>>>>>
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>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Rispetta l'ambiente: se non ti è necessario, non stampare questa mail
>>>>>>
>>>>>>
>>>>>>
>>>>>>           Le informazioni contenute in questa comunicazione e gli
>>>>>> eventuali documenti allegati
>>>>>>
>>>>>>           hanno carattere confidenziale e sono a uso esclusivo del
>>>>>> destinatario. Nel caso
>>>>>>
>>>>>>           questa comunicazione Vi sia pervenuta per errore, Vi informo
>>>>>> che la sua diffusione
>>>>>>
>>>>>>           e riproduzione è contraria alla legge e prego di darmi
>>>>>> prontamente avviso
>>>>>>
>>>>>>           e di cancellare quanto ricevuto. Grazie.
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Rispetta l'ambiente: se non ti è necessario, non stampare questa mail
>>>>>
>>>>>
>>>>>
>>>>>           Le informazioni contenute in questa comunicazione e gli
>>>>> eventuali documenti allegati
>>>>>
>>>>>           hanno carattere confidenziale e sono a uso esclusivo del
>>>>> destinatario. Nel caso
>>>>>
>>>>>           questa comunicazione Vi sia pervenuta per errore, Vi informo
>>>>> che la sua diffusione
>>>>>
>>>>>           e riproduzione è contraria alla legge e prego di darmi
>>>>> prontamente avviso
>>>>>
>>>>>           e di cancellare quanto ricevuto. Grazie.
>>>>>
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>>>
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>>>
>>>
>>>           Le informazioni contenute in questa comunicazione e gli
>>> eventuali documenti allegati
>>>
>>>           hanno carattere confidenziale e sono a uso esclusivo del
>>> destinatario. Nel caso
>>>
>>>           questa comunicazione Vi sia pervenuta per errore, Vi informo
>>> che la sua diffusione
>>>
>>>           e riproduzione è contraria alla legge e prego di darmi
>>> prontamente avviso
>>>
>>>           e di cancellare quanto ricevuto. Grazie.
>>>
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>>
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>
>
>
> --
> Rispetta l'ambiente: se non ti è necessario, non stampare questa mail
>
>
>
>           Le informazioni contenute in questa comunicazione e gli
> eventuali documenti allegati
>
>           hanno carattere confidenziale e sono a uso esclusivo del
> destinatario. Nel caso
>
>           questa comunicazione Vi sia pervenuta per errore, Vi informo
> che la sua diffusione
>
>           e riproduzione è contraria alla legge e prego di darmi
> prontamente avviso
>
>           e di cancellare quanto ricevuto. Grazie.
>
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/faqs/resources/statalist-faq/
> *   http://www.ats.ucla.edu/stat/stata/

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