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

Daryl Morris darylm at uw.edu
Fri Feb 28 02:06:18 CET 2014

```Yes, plotmath contains expressions. The example produced in ?plotmath is
not as complex as the example I provided.  bquote and substitute allow
substitutions of variables ... but what I need to be able to do is
substitute an expression... and that is the magic I'm looking for.

thanks, Daryl

On 2/27/14 3:17 PM, Bert Gunter wrote:
> ?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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