Latex and variables in plot label in R?

Question

How do I use variables in Latex expressions in R?

For example:

plot(X, Y, main=expression(R^2))

Will put R with a nice superscripted 2 as main title.

But let's say I want it to say 'R^2: 0.5', with 0.5 coming from a R variable. How do I do that?

Answer 1

The hack of Owen is pretty cool, but not really the common way to do that. If you use bquote, this is actually pretty easy. bquote will do the same as quote, with the exception that everything between .() will be evaluated in a specified environment (or the global, if nothing is specified).

A trivial example :

X <- 1:10
Y <- 1:10
a <- 0.8
plot(X,Y,main=bquote(R^2 : .(a)))

Gives :

See also ?bquote and ?plotmath for more examples and possibilities