[R] Help with plotmath

[Prof Brian Ripley]

You *parse* strings to form expressions.

plot( c(0,1), c(0,1), main=parse(text=ex) )


On Thu, 10 Jun 2004, Steve Roberts wrote:

> There must be a simple answer. I want to plot an expression, 
> where the expression is held in a string variable. The "obvious" 
> solution along the lines of
> 
> ex<-"x^2"
> plot( c(0,1), c(0,1), main=as.expression(ex) )
> 
> gives me the a title x^2 - ie doesn't treat it like an expression. I 
> suspect I don't understand expressions properly. For the real 
> problem I do need to have my expression string in a variable as it is 
> data-dependent. 

You might also want to explore substitute.

> Can someone tell me the magic words?

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595