Thank you so much for the suggestion. I should simplify my formula.
Kazz

2012/6/22 Achim Zeileis <Achim.Zeileis@uibk.ac.at>

> On Fri, 22 Jun 2012, Kazu Nada wrote:
>
>  Thank you so much for the suggestion.
>> I want to estimate interactions between "the attributes of the choice set"
>> and "subject-specific data (e.g., gender or income)".
>> However, y ~ x | z notation is to see the interaction between "the
>> alternatives of choice set" and "subject-specific data (e.g., gender or
>> income)".
>>
>> Therefore, I need to put the interaction terms after terms suggesting
>> attributes.
>>
>
> Either this is wrong or you did not explain your data properly. (But you
> did not follow the posting guide anyway.)
>
> I suspect that the variables "train", "bus", etc. are 0/1 dummy variables
> indicating the alternative and that variables like "inc" are
> subject-specific covariates. Then you create alternative-specific
> interaction terms which could equivalently and much more conveniently be
> created as subject-specific variables.
>
> Consider the following example with data from the mlogit package:
>
> ## load package and data
> library("mlogit")
> data("Fishing", package = "mlogit")
> Fish <- mlogit.data(Fishing, varying = c(2:9),
>  shape = "wide", choice = "mode")
>
> ## create alternative-specific indicators
> Fish$beach   <- as.numeric(Fish$alt == "beach")
> Fish$boat    <- as.numeric(Fish$alt == "boat")
> Fish$charter <- as.numeric(Fish$alt == "charter")
> Fish$pier    <- as.numeric(Fish$alt == "pier")
>
> ## model with only alternative-specific dummies
> ## your style
> m1a <- mlogit(mode ~ boat + charter + pier | 0, data = Fish)
> ## mlogit style
> m1b <- mlogit(mode ~ 0 | 1, data = Fish)
> cbind(coef(m1a), coef(m1b))
>
> ## model with alternative specific slopes for subject-specific variable
> ## your style
> m2a <- mlogit(mode ~ boat + charter + pier + I(boat*income) +
>  I(charter*income) + I(pier*income) | 0, data = Fish)
> ## mlogit style
> m2b <- mlogit(mode ~ 0 | 1 + income, data = Fish)
> cbind(coef(m2a), coef(m2b))
>
> So I presume that you could greatly simplify your model formula. It might
> be necessary to set up a few of the interactions by hand but I strongly
> suspect not all of them!
>
> hth,
> Z
>
>
>  Any suggestions would be grateful.
>>
>> Kaz
>>
>> 2012/6/8 Achim Zeileis <Achim.Zeileis@uibk.ac.at>
>>      On Fri, 8 Jun 2012, Kazu Nada wrote:
>>
>>            Hi, I need help to do "mlogit" including "l( )
>>            function.
>>            When I put following command,
>>            "Error in  parse(text = x) :  <text>:2:0:" is shown.
>>
>>
>> (1) Your example is not reproducible for us, see the footer of this
>> mail and follow the posting guide.
>>
>> (2) You manually set up a lot of interaction terms which actually can
>> be seen as alternative-specific variables. You can simplify your
>> formula considerably if you use mlogit's y ~ x | z notation. See the
>> two package vignettes for guidance: vignette(package = "mlogit")
>>
>>      --------
>>      res1<-(mlogit(choice~train+**bus+plane+taxi+year+cost
>>      +I(gen*train)+I(gen*bus)+I(**gen*plane)+I(gen*taxi)+I(gen***
>> year)+I(gen*cost)
>>      +I(age*train)+I(age*bus)+I(**age*plane)+I(age*taxi)+I(age***
>> year)+I(age*cost)
>> +I(prep*train)+I(prep*bus)+I(**prep*plane)+I(prep*taxi)+I(**
>> prep*year)+I(prep*c
>>      ost)
>>      +I(inc*train)+I(inc*bus)+I(**inc*plane)+I(inc*taxi)+I(inc***
>> year)+I(inc*cost)
>> +I(tour*train)+I(tour*bus)+I(**tour*plane)+I(tour*taxi)+I(**
>> tour*year)+I(tour*c
>>      ost)
>> +I(ecot*train)+I(ecot*bus)+I(**ecot*plane)+I(ecot*taxi)+I(**
>> ecot*year)+I(ecot*c
>>      ost)
>> +I(kibo*train)+I(kibo*bus)+I(**kibo*plane)+I(kibo*taxi)+I(**
>> kibo*year)+I(kibo*c
>>      ost)
>>      ,data=dat))
>>      --------
>>
>>      I appreciate if you could provide me any suggestion.
>>
>>      Thank you.
>>      Kaz
>>
>>        [[alternative HTML version deleted]]
>>
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>> PLEASE do read the posting guide
>> http://www.R-project.org/**posting-guide.html<http://www.R-project.org/posting-guide.html>
>> and provide commented, minimal, self-contained, reproducible
>> code.
>>
>>
>>
>>

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