[R] How to write "%" before superscript?

[Barry Rowlingson]

Larsen, Thomas wrote:
> I would like to write atom% 15N in the ylab of a plot - "15" should be
> written as superscript. How do I put "%" into the expression? It does
> not work if I type "%" directly after "atom" in the expression below.
> 

string-quote it?

plot(1:10,ylab=expression("atom% "^15*N))


Barry