[R] expressions (nesting, substitution, 2-stage evaluation)

[Bert Gunter]

?plotmath

-- Bert

Bert Gunter
Genentech Nonclinical Biostatistics
(650) 467-7374

"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
H. Gilbert Welch




On Thu, Feb 27, 2014 at 2:58 PM, Daryl Morris <darylm at uw.edu> wrote:
> Hi,
>
> I have a function which generates many plots.  To keep it simple, let's say
> I want to set the main title based on where we are in nested loops.
>
> So, something like
>
> vectorA = c("a","b","c")
> vectorB = c("a","b","c")
>
> for(ii in vectorA) { for(jj in vectorB) {
>   plot(0:1,0:1)
>   title(main = paste(ii,jj))
> }
>
> that part is easy!   The question is what if I wanted vectorA to be an
> expression?
>
> I'd like to be able to set vectorA =
> c(expression(paste("TNF-",alpha)),expression(paste("IFN-",gamma))), and have
> the plot title show the greek letters.
>
> Obviously, in the for-loop I could build the expression all at once, but
> there are lots of programmatic reasons I'd like to be able to have this
> program structure.  Is there a solution which modifies either/both (1) the
> setting of main in the loop (2) how I define the vector outside of the loop?
>
>
> thanks, Daryl
>
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