[R] Analysis of ordinal categorical data

[John Fox]

Dear Thomas,

Barring a numerical problem, polr() will fit the model as a mechanical
matter, but the proportional-odds model and other, relatively parsimonious,
models for ordinal data, make assumptions about the structure of the data. I
don't think that it's sensible to explain the model in detail here; you
could consult a text that discusses the model -- it's a standard topic in
categorical-data analysis. Two sources are Venables and Ripley's Modern
Applied Statistics with S (with which the MASS package is associated) and my
own R and S-PLUS Companion to Applied Regression. 

Regards,
 John

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of 
> thsudler at swissonline.ch
> Sent: Wednesday, May 05, 2004 9:29 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Analysis of ordinal categorical data
> 
> Thanks a lot for your advice. What do you mean with "the 
> proportional-odds assumption may not hold"? Does this 
> solution with "polr" always works? Or what's important to 
> take into account?
> 
> Regards
> Thomas
> 
> >Dear Thomas,
> >
> >One approach to an ordinal response variable is the 
> proportional-odds 
> >model, implemented in the MASS package as polr(). The 
> proportional-odds 
> >>assumption may not hold, however.
> >
> >I hope this helps,
> > John
> >
> > -----Original Message-----
> > From: r-help-bounces at stat.math.ethz.ch 
> > [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of 
> > thsudler at swissonline.ch
> > Sent: Wednesday, May 05, 2004 7:45 AM
> > To: r-help at stat.math.ethz.ch
> > Subject: [R] Analysis of ordinal categorical data
> > 
> > Hi
> > 
> > I would like to analyse an ordinal categorical variable. I 
> know how I 
> > can analyse a nominal categorical variable (with multinom 
> or if there 
> > are only two levels with glm).
> > 
> > Does somebody know which command I need in R to analyse an ordinal 
> > categorical variable?
> > 
> > I want to describe the variable y with the variables 
> x1,x2,x3 and x4. 
> > So my model looks like: y ~ x1+x2+x3+x4.
> > 
> > y: ordinal factor variable with levels (never, rare, 
> bychance, often).
> > 
> > Thanks a lot in advance
> > Thomas
> > 
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide! 
> > http://www.R-project.org/posting-guide.html
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html