[R] Expressions in plots

[Uwe Ligges]

David Marchette wrote:
> 
> Perhaps there is an obvious answer to this,
> but I can't seem to figure it out. I want to
> generate a sequence of plots, where a variable
> (say x) is changed from plot to plot. For each
> plot I'd like to have a title indicating the value
> of x. However, what I really want is to use
> expression to typeset some math. A simple
> example is I'd like to do something like
> expression(mu==x), where instead of the string "x"
> I'd like it to put the value of x (2.35, say).
> I can't figure out how to do this. Obviously
> I could treat each value individually and type
> in 2.35, etc, but I'd like to do this a little
> more elegantly, especially since I want to change
> the values of x quite a bit to explore some
> property. The closest I have come is to use
> paste: qq <- paste("expression(mu==",x,")",sep="")
> but can't figure out how to turn qq from a string
> to an expression. Thanks for any suggestions.

Try the nice function substitute(.), e.g.:

  x <- 2.35
  plot(1:10, main=substitute(mu==x, list(x=x)))

Regards,
Uwe Ligges
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