David Winsemius <dwinsem...@comcast.net> wrote >I always assumed that the intercept was zero and the slope = unity. > > y <- rt(200, df = 5) > qqnorm(y); qqline(y, col = 2) > qqplot(y, rt(300, df = 5)) > abline(0, 1, col="red") >
Suppose you have the following x <- rnorm(500) y <- 500*(x + runif(500, 0,1)) qqplot(x,y) Then an abline(0,1) will not be useful; it will be an almost horizontal line. But m1 <- lm(y~x) abline(coef(m1)) does the trick. Peter Peter L. Flom, PhD Statistical Consultant Website: www DOT peterflomconsulting DOT com Writing; http://www.associatedcontent.com/user/582880/peter_flom.html Twitter: @peterflom ______________________________________________ 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.
