Hi I actually do not know what you are talking about. I believe that the code I provided works (if i did not make typing mistake), but you failed to provide data to test so I made my own data and subset inside lm works as expected.
fake<-data.frame(weight<-rnorm(15), length=weight*3+rnorm(15), sex=rep(c("b","g"), c(7,8))) names(fake)[1]<-"weight" plot(fake$length, fake$weight, col=as.numeric(fake$sex)) bl<-lm(weight~length, data=fake, subset=sex=="b") abline(bl) gl<-lm(weight~length, data=fake, subset=sex=="g") abline(gl, col=2) Beware that R is smart but not smart enough to correct user typing mistakes (missing parntheses, missing commas, etc.). Typing mistakes are probably the most common source of failing code. Regards Petr > -----Original Message----- > From: Elaine Kuo [mailto:elaine.kuo...@gmail.com] > Sent: Tuesday, January 08, 2013 2:03 AM > To: PIKAL Petr > Cc: r-help@r-project.org > Subject: Re: [R] plot xaxp issue > > Hello, > > I figured out that the code should be > > boyline<-lm(body_weight ~ body_length, data=subset > (together,,sex=="boy")) > > However, the "" could be omitted if the field name happened to be > numeric, such as 1, 2, or 3. > Please kindly explain why the "" could be omitted for numbers. > Thanks again. > > Elaine > On Tue, Jan 8, 2013 at 8:40 AM, Elaine Kuo <elaine.kuo...@gmail.com> > wrote: > > boyline<-lm(body_weight ~ body_length, data=together, > > subset(together,sex=="boy")) ______________________________________________ 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.