Plotmath bug or my misunderstanding?

Hello,

It seems like a "feature". When trying the example below with more
atops, the two bottom most lines, and only those two lines, feature
character expansion relative to the default size and relative to the
line before last.

plot(1, type="n", xaxt='n', yaxt='n', ann=FALSE, xlim=c(-0.5, 6))
text(1, 1,labels=expression(atop(atop(sigma,"some text"),
"another level")), cex = 2)
text(3, 1, labels=expression(atop(atop(atop(sigma,"some text"),
"another level"), "third")), cex = 2)
text(5, 1, labels=expression(atop(atop(atop(atop(sigma,"some text"),
"another level"), "third"), "4th")), cex = 2)

Anyway, I couldn't find this behavior in the help pages.

Rui Barradas


Em 13-05-2012 11:00, Bert Gunter escreveu:

Date: Sat, 12 May 2012 14:05:26 -0700
From: Bert Gunter<gunter.berton at gene.com>
To:r-help at r-project.org
Subject: [R] Plotmath bug or my misunderstanding?
Message-ID:
<CACk-te0syHj9XjbkfHPYtCMwyWtYdPFYCehxGpxidtBR0_PkdQ at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

This is a followup to a recent post on using atop() to obtain
multiline expressions.

My reading of the plotmath docs makes it clear that issuing (in base
graphics) the specification

par(cex = 2)

doubles symbols and regular text in subsequent plotmath expressions.
However, it is unclear to me what specifying cex_within_ the
annotation function using plotmath should do, and the following seems
to want to have it both ways: ignore/obey )or maybe recycle?)

plot(1,type="n", xaxt='n', yaxt='n', ann=FALSE)
text(1,1,labels=expression(atop(sigma,"some text")),cex = 2)
## obeys the cex specification in symbols and text

HOWEVER

plot(1,type="n", xaxt='n', yaxt='n', ann=FALSE)
text(1,1,labels=expression(atop(atop(sigma,"some text"),"another
level")),cex = 2)
## ???

For even more fun, try:

plot(1,type="n", xaxt='n', yaxt='n', ann=FALSE)
text(1,1,labels=expression(atop(atop(sigma,"some text"),"another
level")),cex = 1:2)
##????

So I confess to being flummoxed. Enlightenment would be much appreciated.

Cheers,
Bert