On Fri, 12 Jan 2007, Tom Backer Johnsen wrote: > My simpleminded understanding of simple regression is that when > plotting regression lines for x on y and y on x in the same plot, the > lines should cross each other at the respective means. But, given the > R function below, abline (lm(y~x)) works fine, but abline (lm(x~y)) > does not. Why? > > function () { > attach (attitude) > x <- rating > y <- learning > detach (attitude) > plot (x, y) > abline(v=mean(x)) > abline(h=mean(y)) > abline (lm(y~x)) > abline (lm(x~y)) > }
The axes are getting reversed: xylm <- lm(x~y) newdata <- data.frame(y=0:80) lines(predict(xylm, newdata), newdata$y, col="blue") gets them back. Roger > > ______________________________________________ > R-help@stat.math.ethz.ch 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. > -- Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 e-mail: [EMAIL PROTECTED] ______________________________________________ R-help@stat.math.ethz.ch 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.