Dear Peter and Anthony, Thanks, Peter, for answering the question, but scatterplot() should work even if z is not a factor, and does for me in the following example:
> library(car) > Prestige$tp <- with(Prestige, ifelse(type == "prof", 1, 0)) > scatterplot(prestige ~ income | tp, data=Prestige) So, Anthony, the usual advice about providing a reproducible example seems applicable here. Regards, John -------------------------------- John Fox Senator William McMaster Professor of Social Statistics Department of Sociology McMaster University Hamilton, Ontario, Canada web: socserv.mcmaster.ca/jfox > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf Of Peter Ehlers > Sent: April-24-10 11:57 PM > To: Anthony Lopez > Cc: R-help@r-project.org > Subject: Re: [R] categorical variable in scatterplot (car) > > On 2010-04-24 21:30, Anthony Lopez wrote: > > Hello R folks, > > > > I am encountering a problem with the following scatterplot function from > the > > car package: > > > >> scatterplot(y~x|z) > > > > where y and x are continuous (interval) random variables and z is a > > categorical variable. When z is a categorical variable coded 1 or 2, I > > (appropriately) get a scatterplot of y by x, coded by z. Similarly, when z > > is a categorical variable coded 1, 2, or 3, there is again, no problem. > > However, when z is a categorical variable coded 0 or 1, the scatterplot > > > >> scatterplot(y~x|z) > > > > is exactly identical to the one generated by > > > >> scatterplot(y~x) > > > > It is not possible that this is due to the fact that there is no difference > > between the categories. It is as if R doesn't "see" that I want it coded > by > > z. But this only happens when one of the categories of z is coded "0" > (i.e. > > zero). Any ideas why this is so, or how I can fix this without recoding my > > variable? > > Make z a factor (which it really should be anyway). > > -Peter Ehlers > > > > > Thank you! > > > > Anthony > > > > [[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. > > > > > > -- > Peter Ehlers > University of Calgary > > ______________________________________________ > 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. ______________________________________________ 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.
