Den Fr, 2007-02-02, 06:03 skrev Stacey Buckelew: > Hi, > > I am working on a regression tree in Rpart that uses a continuous response > variable that is ordered. I read a previous response by Pfr. Ripley to a > inquiry regarding the ability of rpart to handle ordinal responses in > 2003. At that time rpart was unable to implement an algorithm to handle > ordinal responses. Has there been any effort to rectify this in recent > years?
The `ctree' function in the `party' package is able to handle ordered responses, but note that there are fundamental differences between the former and `rpart'. Reading the package vignette and the relevant references will help. However, at the moment there seems to be a problem related to the ordinal case (predicted probabilities > 1) and I've CC:ed the package's maintainer (Torsten Hothorn). HTH, Henric - - - - - Torsten, consider the following: > ### ordinal regression > mammoct <- ctree(ME ~ ., data = mammoexp) Warning message: no admissible split found > ### estimated class probabilities > treeresponse(mammoct, newdata = mammoexp[1:5, ]) [[1]] [1] 1.822115 [[2]] [1] 1.265487 [[3]] [1] 1.822115 [[4]] [1] 1.560440 [[5]] [1] 1.822115 > sessionInfo() R version 2.4.1 Patched (2007-01-06 r40399) i386-pc-mingw32 locale: LC_COLLATE=Swedish_Sweden.1252;LC_CTYPE=Swedish_Sweden.1252;LC_MONETARY=Swedish_Sweden.1252;LC_NUMERIC=C;LC_TIME=Swedish_Sweden.1252 attached base packages: [1] "stats4" "grid" "splines" "stats" "graphics" "grDevices" [7] "utils" "datasets" "methods" "base" other attached packages: party vcd colorspace MASS strucchange sandwich "0.9-8" "1.0-2" "0.95" "7.2-31" "1.3-1" "2.0-1" zoo coin mvtnorm modeltools survival "1.2-2" "0.5-2" "0.7-5" "0.2-10" "2.30" > > > Thanks! > > Stacey > > > > On Mon, 2 Jun 2003, Andreas Christmann wrote: >> >>> 1. RE: Ordinal data - Regression Trees & Proportional Odds >> (Liaw, Andy) >> >> > AFAIK there's no implementation (or description) of tree algorithm >> > that handles ordinal response. >> > >> >> Regression trees with an ordinal response variable can be computed with >> SPSS Answer Tree 3.0. > They *can* be handled by tree or rpart in R. > I think Andy's point was that there is no consensus as to the right way to > handle them: certainly using the codes of categories works and may often > be reasonable, and treating ordinal responses as categorical is also very > often perfectly adequate. > Note that rpart is user-extensible, so it would be reasonably easy to > write > an extension for a proportional-odds logistic regression model, if that is > thought appropriate (and it seems strange to me to impose such strong > structure on the model with such a general `linear predictor': POLR > models are often in my experience a poor reflection of real problems). > -- > Brian D. Ripley, [EMAIL PROTECTED] > 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 272860 (secr) > Oxford OX1 3TG, UK Fax: +44 1865 272595 > > ______________________________________________ > R-help@stat.math.ethz.ch 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. > > ______________________________________________ R-help@stat.math.ethz.ch 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.