[R] Problem in using confint method on polr model object

[Prof Brian Ripley]

On Wed, 3 May 2006, Ulrich Halekoh wrote:

> I fit a proportional odds model
> with the polr-function of the MASS package from
> Venables and Ripley
>
>
> Applying the confint method to  calculate confidence intervals for the
> parameters I get
> the following error message
>
>
> Waiting for profiling to be done...
> Re-fitting to get Hessian
> Error in X[, -i, drop = FALSE] : incorrect number of dimensions
>
> Can someone explain the error-message?

This is a single-coefficient model, and in profile.polr
it needs to be

     X <- model.matrix(fitted)[, -1, drop = FALSE]



>
> (The data are from McCullagh (1980), JRSS,B)
>
>
>
> tonsiles<-data.frame(carrier=factor(rep(c('yes','no'),each=3)),
>                     size=ordered(rep(c(1,2,3),2)),
>                     count=c(19,29,24,497,560,269))
> library(MASS)
> m<-polr(size~carrier,data=tonsiles,weights=count)
> confint(m)
>
>
> Ulrich
>
>
> platform       i386-pc-mingw32
> arch           i386
> os             mingw32
> system         i386, mingw32
> status
> major          2
> minor          3.0
> year           2006
> month          04
> day            24
> svn rev        37909
> language       R
> version.string Version 2.3.0 (2006-04-24)
>
>
> Ulrich Halekoh
> Danish Institute of Agricultural Sciences
> Unit of Statistics and Decision Analysis
> Denmark
>
>
> 	[[alternative HTML version deleted]]
>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
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