Hi Peter, Thanks for the example. It was previously pointed out to me (in a private message) that the legend wasn't printed by scatterplot() when the groups variable isn't numeric. In fixing that, I also took care of the problem that you noticed. The fix is (or actually will be shortly) in the development version of the car package on R-Forge, which will be released sometime this spring or summer.
Thanks again, John > -----Original Message----- > From: Peter Ehlers [mailto:ehl...@ucalgary.ca] > Sent: April-25-10 1:20 PM > To: John Fox > Cc: 'Anthony Lopez'; R-help@r-project.org > Subject: Re: [R] categorical variable in scatterplot (car) > > Hi John, > > The problem seems to be with the order in which the 'levels' of > the conditioning variable appear. Here's a reproducible example: > > Prestige$tp<- with(Prestige, ifelse(type == "prof", 0, 1)) > scatterplot(prestige ~ income | tp, data=Prestige) > > Note that I've just switched the 0/1 from your example. > > A quick look at scatterplot.formula suggests that wrapping > the 'X[, 3]' in this line > > scatterplot(X[, 2], X[, 1], groups = X[, 3], xlab = xlab, > > inside an as.factor() would solve the problem. > > -Peter > > > On 2010-04-25 8:40, John Fox wrote: > > Dear Peter and Anthony, > > > > Thanks, Peter, for answering the question, but scatterplot() should work > > even if z is not a factor, and does for me in the following example: > > > >> library(car) > >> Prestige$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. > > > > > > > > -- > 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.
