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

[Gabor Grothendieck]

I cannot explain it but I must have come across it since
I noticed in various places in some of my code I have
used, in terms of your example, the following:

plot(y ~ x, main = as.expression(bquote(m[1] == .(a))))

plot(y ~ x, main = list(bquote(m[1] == .(a))))

both of which work as expected.

On 2/9/06, Berton Gunter <gunter.berton at gene.com> wrote:
>
> 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
>
>
> -- Bert Gunter
> Genentech Non-Clinical Statistics
> South San Francisco, CA
>
> "The business of the statistician is to catalyze the scientific learning
> process."  - George E. P. Box
>
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