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

[David Winsemius]

On Feb 27, 2014, at 3:17 PM, Bert Gunter wrote:

> ?plotmath
> 
> -- Bert

Daryl;; 

I think what Bert was hoping you would do was read the plotmath page and figure it out on your own but that can be a bit tricky when working with expression object vectors. Here is (perhaps) a step forward:

vectorA = c( bquote("TNF-"*alpha), bquote("IFN-"*gamma) )

for(ii in vectorA)  {
  plot(0:1,0:1)
  title(main = ii)
 } 

Now as Jim Holtman is fond of saying... what problem were you (really) trying to solve?

-- 
David.

> 
> 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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>> and provide commented, minimal, self-contained, reproducible code.
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius
Alameda, CA, USA