[R] combining mathematical notation and value substitution

[Uwe Ligges]

Faheem Mitha wrote:
> Dear People,
> 
> I need to make a label which both contains math notation as well as
> substitutes a value for an object. In the following label, len and theta
> are one dim variables, and I am substituting their values appropriately.
> This label looks fine except that I want the greek symbol for theta to
> appear instead of the word `theta'. How can I do so most easily? I don't
> understand the underlying mechanisms well enough to work it out for
> myself. Thanks in advance.
> 
> Please cc me. I'm not subscribed to the list.
> 
>                                                            Faheem.
> 
> main=paste("Monotonic Multigamma run (n=",
> deparse(substitute(len)),", ",
> expression(theta),"=", deparse(substitute(theta)),").")

No, it won't work that way, because you have to specify an S expression 
in order to get mathematical annotation. An expression within paste() 
will be converted to a character string.

What you ca do is the other way round:


t1 <- theta     # you cannot use theta as variable and math. symbol
plot(1:10, main =
   substitute("Monotonic Multigamma run (" * n  == len * ", " *
     theta == t1 * ").", list(len = len, t1 = t1)))


See also ?plotmath or that small article in R News:
Ligges (2002): R Help Desk: Automation of Mathematical Annotation in 
Plots. R News 2(3), 32-34.

Uwe Ligges