Also posted as http://stats.stackexchange.com/questions/7720/how-to-understand-output-from-rs-polr-function-ordered-logistic-regression .
Also, I read section 7.3 of "Modern Applied Statistics with S" by Venables and Ripley (who wrote polr?), and I can still not answer many of these questions. On Tue, Mar 1, 2011 at 3:25 PM, Dan Frankowski <dfran...@gmail.com> wrote: > I am new to R, ordered logistic regression, and polr. > > The "Examples" section at the bottom of the help page for > polr<http://stat.ethz.ch/R-manual/R-patched/library/MASS/html/polr.html>(that > fits a logistic or probit regression model to an ordered factor > response) shows > > options(contrasts = c("contr.treatment", "contr.poly")) > > house.plr <- polr(Sat ~ Infl + Type + Cont, weights = Freq, data = housing) > > pr <- profile(house.plr) > > plot(pr) > pairs(pr) > > > - > > What information does pr contain? The help page on > profile<http://stat.ethz.ch/R-manual/R-patched/library/stats/html/profile.html>is > generic, and gives no guidance for polr. > - > > What is plot(pr) showing? I see six graphs. Each has an X axis that is > numeric, although the label is an indicator variable (looks like an input > variable that is an indicator for an ordinal value). Then the Y axis is > "tau" which is completely unexplained. > - > > What is pairs(pr) showing? It looks like a plot for each pair of input > variables, but again I see no explanation of the X or Y axes. > - > > How can one understand if the model gave a good fit? > summary(house.plr)shows Residual Deviance 3479.149 and AIC (Akaike > Information Criterion?) of > 3495.149. Is that good? In the case those are only useful as relative > measures (i.e. to compare to another model fit), what is a good absolute > measure? Is the residual deviance approximately chi-squared distributed? > Can > one use "% correctly predicted" on the original data or some > cross-validation? What is the easiest way to do that? > - > > How does one apply and interpret anova on this model? The docs say > "There are methods for the standard model-fitting functions, including > predict, summary, vcov, anova." However, running anova(house.plr)results > in anova > is not implemented for a single "polr" object > - > > How does one interpret the t values for each coefficient? Unlike some > model fits, there are no P values here. > > I realize this is a lot of questions, but it makes sense to me to ask as > one bundle ("how do I use this thing?") rather than 7 different questions. > Any information appreciated. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
