[R] superscript characters in title with '+'

[David Winsemius]

On Oct 22, 2010, at 7:01 AM, DrCJones wrote:
>
> Hi,
>
> How can I get the '2+' into superscript in the following title:
>
> '[Ca2+]i onsets'
>
> I tried the command below, but it doesn't work. What am I missing?

The first is an unambiguous description of what you want, but here are  
some guesses (since it was entirely confusing when above you put the  
"i" after the rt-square-bracket, and below put it before the "2+"):

expression("["*Ca*"]"*i^paste(2,"+")~'onsets')
expression("["*Ca*"]"^paste(2,"+")*i~'onsets')

If one of those guesses is correct then what you were missing was an  
understanding of the differences between the plotmath syntax and  
regular printing. The characters"[", "]", and "+" are special so if  
you just want them treated as ordinarily characters, you need to  
surround them in quotes. If you want to put "2+" as superscript, the  
plotmath paste function (not to be confused with the ordinary R  
paste() ) will let you group sub-expressions. It would also be  
possible to use the group() expression-function. And the final missing  
piece is the knowledge that itmes in an expression are separated by  
"*"'s and "~"'s rather than commas or spaces.

?plotmath  # which I think does an inadequate job of describing the  
features mentioned above.

If you need to insert values in expressions then:  ?bquote   or  ? 
substitute

Took me a couple of years to feel that I had a decent chance of  
getting an expression correct on even the second or third try.

>
> hist(X, main=expression(([Ca*]i^2+) 'onsets'),  xlab = 'sec')
>
>

David Winsemius, MD
West Hartford, CT