[R] Reading expressions from character vectors

[Charilaos Skiadas]

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?

I suppose the problem is that the result of as.expression(labels) is  
expression("-infinity", "infinity") instead of expression(-infinity,  
infinity), as I would have liked.  I just can't figure out how to  
convert it to the right thing.

Haris