[R] Regression lines

Tom Backer Johnsen backer at psych.uib.no
Fri Jan 12 10:39:23 CET 2007

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 (lm(y~x))
abline (lm(x~y))

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