[R] "main" parameter in plot.default vs plot.formula

From: Berton Gunter <gunter.berton_at_gene.com>
Date: Fri 10 Feb 2006 - 05:00:07 EST

Folks:

R 2.2.0 on Windows.

I find the following somewhat puzzling:

> a<-1; x<-0:1; y<-x

## following works fine:
> plot(x,y ,main= bquote(n[1] == .(a) ))

## following produces an error:
> plot(y~x ,main= bquote(n[1] == .(a) ))
Error in paste(n[1] == 1, " and ", n[2] == 2) : object "n" not found


Note 1: I assume that this is due to the following documented behavior of plot.formula():

"Both the terms in the formula and the ... arguments are evaluated in data enclosed in parent.frame() if data is a list or a data frame."

Nevertheless, the behavior seems inconsistent to me. Am I missing something (including the "I assume ..." comment)?

Note 2: If one uses substitute() instead, it works fine:

plot(y~x ,main= substitute(bquote(n[1] == a),list(a=a)))

Any illumination, public or private, would be appreciated.

Cheers,
Bert  

"The business of the statistician is to catalyze the scientific learning process." - George E. P. Box



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