[R] problems with MNP

[Kosuke Imai]

Hi Joan,
  You need to do:
                                                                                      
 res1 <- mnp(PREVOTE3 ~ 1, choiceX = list("1"=UCLC, "2"=UDLC, "3"=UPLC),
             cXnames = "ut", data = small, verbose = TRUE)
                                                                                      
The quotations for "1" etc. are necessary because those are names of the
list elements. Also, you should check the convergence of the Markov chain
as 500 draws is typically not. In our Journal of Statistical Software
paper (available at http://www.princeton.edu/~kimai/research/MNP.html), we
show how to do this through some examples.

Best,
Kosuke
                                                                                      
---------------------------------------------------------
Kosuke Imai               Office: Corwin Hall 041
Assistant Professor       Phone: 609-258-6601
Department of Politics    eFax:  973-556-1929
Princeton University      Email: kimai at Princeton.Edu
Princeton, NJ 08544-1012  http://www.princeton.edu/~kimai
---------------------------------------------------------

> > From: Joan Serra <jserra at uchicago.edu>
> > Date: July 13, 2005 6:14:31 AM PDT
> > To: r-help at stat.math.ethz.ch
> > Subject: [R] problems with MNP
> >
> >
> > Hi all,
> >
> > Does anybody have a hint on what may be going wrong in this R code? I
> > mimic the sample code from the MNP developers but I seem unable to  
> > get the
> > choice specific variables right.
> >
> > Thanks,
> > Joan Serra
> >
> >
> >> rm(list=ls())
> >> library(foreign)
> >> small<-read.spss("small.sav")
> >>
> > Warning message:
> > small.sav: Unrecognized record type 7, subtype 13 encountered in  
> > system
> > file.
> >
> >> library(MNP)
> >>
> > MNP: R Package for Fitting the Multinomial Probit Models
> > Version: 1.3-1
> > URL: http://www.princeton.edu/~kimai/research/MNP.html
> >
> >>
> >>      res1 <- mnp(PREVOTE3 ~ 1, choiceX = list(1=UCLC, 2=UDLC,  
> >> 3=UPLC),
> >>
> > Error: syntax error
> >
> >>                  cXnames = "ut", data = small, n.draws = 500,  
> >> burnin =
> >>
> > 100,
> > Error: syntax error
> >
> >>                  verbose = TRUE)
> >>
> > Error: syntax error
> >
> >>
> >> # another try giving arbitrary names to the values of the dependent
> >>
> > variable
> >
> >>
> >>      res1 <- mnp(PREVOTE3 ~ 1, choiceX = list(Clinton=UCLC,  
> >> Dole=UDLC,
> >>
> > Perot=UPLC),
> > +                  cXnames = "ut", data = small, n.draws = 500,  
> > burnin =
> > 100,
> > +                  verbose = TRUE)
> >
> > The base category is `1'.
> >
> > The total number of alternatives is 3.
> >
> > Error in xmatrix.mnp(formula, data = eval.parent(data), choiceX =
> > call$choiceX,  :
> >          Error: Invalid input for `choiceX.'
> >   Some variables do not exist.
> >
> >>
> >> # another try using a string type dependent variable
> >>
> >>      res1 <- mnp(PRVOTE3 ~ 1, choiceX = list(Clinton=UCLC, Dole=UDLC,
> >>
> > Perot=UPLC),
> > +                  cXnames = "ut", data = small, n.draws = 500,  
> > burnin =
> > 100,
> > +                  verbose = TRUE)
> > Error in model.frame(formula, rownames, variables, varnames, extras,
> > extranames,  :
> >          invalid variable type
> >
> >>
> >>
> >
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> >
> 
> 
> --
> Andrew D. Martin, Ph.D.
> Associate Professor of Political Science
> Director, Program in Applied Statistics and Computation
> Professor of Law (by courtesy)
> Washington University in St. Louis
> 
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