[R] sub- and superscript in plot labels

[Prof Brian Ripley]

On Thu, 4 Nov 2004, Gavin Simpson wrote:

> Dear List,
> 
> I need to add a subscript and a superscript to some of the ions in the 
> labels on some plots.
> 
> I have got to here but now I'm stuck:
> 
> plot(1:10, xlab = expression(paste("nm SO"[4], " ", mu, "eq cm"^{-2}, " 
> yr"^{-1})))
> 
> Which gives almost  what I require. No matter what I tried, however, I 
> could not get bot a sub script *and* a superscript attached to the SO in 
> the label.
> 
> In LaTeX I would just do $SO_4^{2-}$ but taking that to R produces a 
> syntax error:
> 
> plot(1:10, xlab = expression(paste("nm SO"[4]^{2-}, " ", mu, "eq 
> cm"^{-2}, " yr"^{-1})))

The problem is 2-.  That's not an R expression.  Using "2-" might give
what you want, but it will use a hyphen rather than a minus. Otherwise

plot(1:10, xlab = expression(paste("nm SO"[4]^{2-phantom()})))

will give a minus.

-- 
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