[R] Sweave and echoing R comments

Frank E Harrell Jr f.harrell at vanderbilt.edu
Sun Jun 20 22:34:50 CEST 2004

Charles H. Franklin wrote:
> Is there any way to echo comments from an R source file into an 
> SWeave->LaTeX document?
> Example:
> # Npop is population total
> # Npoph0..Npoph2 are stratum totals
> # Npoph is vector of stratum totals
> Npop<-sum(to2000)
> Npoph0<-sum(to2000[bg==0])
> Npoph1<-sum(to2000[bg==1])
> Npoph2<-sum(to2000[bg==2])
> Npoph<-c(Npoph0,Npoph1,Npoph2)
> In the final LaTeX document, I'd like the comments to be echoed so 
> readers other than me have guidance about variable names etc.
> I suppose advocates of literate programming might argue that if the 
> comment is important it should be in the body of the .snw file, not 
> merely as R comments. Still... it seems easier to use brief comments in 
> the code itself and more explanatory text in the body of the document.
> Searches of "Sweave" and "comment" in the list and documentation didn't 
> turn up anything about echoing comments in either R or Sweave.
> Thanks.
> Charles

I agree that it would be nice to see comments in the output.  I hope 
that Fritz Leisch will consider adding a hook that is a user-provided R 
function that take vectors of character strings representing a chunk of 
code and generating any desired LaTeX markup for pretty printing of the 
code.  The function would return character vectors in LaTeX format.  I 
like comments to appear in a smaller font, and for certain character 
translations, such as <- being replaced with a left arrow.

Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University

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