Re: [R] Regression lines

From: Uwe Ligges <ligges_at_statistik.uni-dortmund.de>
Date: Fri 12 Jan 2007 - 10:10:21 GMT

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?

Well, abline() in fact plots a line using the estimated coefficients for intercept and slope and assumes you have plotted LeftHandSideOfFormula against RightHandSideOfFormula.
If you did vice versa, abline() does not respect your mistake.

Uwe Ligges

> 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))
> }
>
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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. Received on Fri Jan 12 21:19:53 2007

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