Thank you both for your helpful reply! And apologies for the lack of a reproducible example - I would/could send one now, but I believe Peter's example will suffice (and thank you for that). And making z a factor worked perfectly. Thank you!
Anthony On Sun, Apr 25, 2010 at 10:20 AM, Peter Ehlers <ehl...@ucalgary.ca> wrote: > 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 > [[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.
