[R] Reading expressions from character vectors

[hadley wickham]

On 2/4/07, Charilaos Skiadas <skiadas at hanover.edu> wrote:
> Greetings,
>
> I have a problem that I am sure is very straightforward, but I just
> can't wrap my head around it. I've read the help pages on text,
> plotmath, expression, substitute, but somehow I can't find the answer
> to this simple question.
>
> Basically consider the following example:
>
> plot( NULL, xlim = c(0,2), ylim = c(0,2) )
> expressions <-  expression( -infinity, infinity )
> text( c(0.5,1.5), 1.5, expressions )
> labels <- c( "-infinity", "infinity" )
> text( c(0.5,1.5), 0.5, as.expression(labels) )
>
> I want the character vector "labels" to be interpreted as  an
> expression vector, and so to appear just like the expressions vector.
> Is this possible? I mean yes, it is probably possible, but how?

text( c(0.5,1.5), 0.5, parse(text=labels))  ?

You need to parse the text to get to the expression

Hadley