I think the problem is that plot's log axes are to the base 10 so the lm() call needs to use log10, not log. E.g.,
x<-101:200 y<-sqrt(x)+1+runif(100) plot(x,y,log="xy") abline(col="red", lm(log(y)~log(x))) # nothing plotted abline(col="blue", lm(log10(y)~log10(x))) # passes through points Expand the y axis a bit and you can see where the base-e line went: plot(x,y,log="xy", ylim=c(1,100)) abline(col="red", lm(log(y)~log(x))) # plotted well above the points abline(col="blue", lm(log10(y)~log10(x))) # passes through points Bill Dunlap TIBCO Software Inc - Spotfire Division wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of stephen sefick > Sent: Thursday, June 04, 2009 10:04 AM > To: Par Leijonhufvud > Cc: R-help > Subject: Re: [R] Plot and lm > > Could you provide a reproducible example even with fake data would be > fine or dput() yours. > > On Thu, Jun 4, 2009 at 10:11 AM, Par Leijonhufvud > <p...@hunter-gatherer.org> wrote: > > I want to make a log-log plot with a regression line, but I > can't figure > > out what I'm doing wrong. What I'm trying is: > > > > plot(mass,area, log="xy", pch=as.numeric(food)) > > abline(lm(mass~area)) > > > > or > > > > plot(mass,area, log="xy", pch=as.numeric(food)) > > islands$logmass <- log(mass) > > islands$logarea <- log(area) > > attach(islands) > > abline(lm(logmass~logarea)) > > > > > > But that does not show a line. Where am I going wrong? > > > > data: > > island, area,species,food,mass > > Ibiza , 577 , Anser n. sp., herb, 2.0 > > Ibiza , 577 , Haliaeetus albicilla, carn, 4.8 > > Mauritius , 1874 , Raphus cucullatus, herb, 19 > > Mauritius , 1874 , Circus alphonsi, carn, 0.63 > > Mallorca , 3667 , Myotragus balearicus, herb, 40 > > Mallorca , 3667 , Aquila chrysaetos, carn, 4.2 > > Kreta , 8259 , Elephas creutzburgi, herb, 3200 > > ....... > > > > /Par > > > > -- > > Par Leijonhufvud > p...@hunter-gatherer.org > > I don't believe in reincarnation. I used to, > > but that was in another life. > > > > ______________________________________________ > > 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. > > > > > > -- > Stephen Sefick > > Let's not spend our time and resources thinking about things that are > so little or so large that all they really do for us is puff us up and > make us feel like gods. We are mammals, and have not exhausted the > annoying little problems of being mammals. > > > -K. Mullis > > ______________________________________________ > 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.
