On Tue, 2009-07-14 at 15:57 -0700, Michael wrote: > Hi all, > > Could anybody tell me what happened to my logistic regression in R? > mylog=glm(mytraindata$V1 ~ ., data=mytraindata, family=binomial("logit")) > > It generated the following error message: > > Error in model.frame.default(Terms, newdata, na.action = na.action, > xlev = object$xlevels) : > factor 'state1' has new level(s) AP
Hi Michael, I am 99.9% certain that what you claim above is completely false. That error looks to arise from a call in predict.lm which is called when you use predict.glm The big give away for me was 'newdata' in the call that produced the error. That suggested to me you were using a predict method. I then tracked down a potential source of the error by looking at what happens when you call predict on a "glm" object. Members of the list shouldn't have to do this to help answer posts to the list. The posting guide asks you to provide, minimal, self-contained, reproducible examples. And failing that, the R code you actually used. After the chastisement ;-) some help: 1) I'm guessing, but in the dataset that you predict for, does the state1 variable have more/different levels to the training data? Try levels(mytraindata) and levels(mytestdata) where mytestdata is the data you supplied as 'newdata' in your call to predict. 2) Your glm call contains some redundancy. It can be simplified to: mylog <- glm(V1 ~ ., data = mytraindata, family = binomial) Realising that the logit link is the default in the binomial family, and if you specify data you don't need to refer to the data object in the formula. HTH G -- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Dr. Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% ______________________________________________ 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.