[R-sig-ME] Unexpected text-output using BY to plot random effects.

Sebastian P. Luque spluque at gmail.com
Tue Sep 16 16:13:14 CEST 2008

On Tue, 16 Sep 2008 15:27:36 +0200,
Dimitris Rizopoulos <d.rizopoulos at erasmusmc.nl> wrote:

> abline() does not return anything, it justs adds lines to the existing
> plot; this is why you obtain NULL from the by() statement. One option
> to avoid printing is to use invisible(), e.g.,

> invisible(by(sleep, sleep$resp, function(x) abline(coef=x)))

Also, make sure you're using abline correctly here.  Especially, read
about the 'coef' argument.


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