[R] Sweave: looping over mixed R/LaTeX code

[Jeffrey Horner]

Stephan Kolassa wrote on 06/13/2008 03:22 AM:
> Dear guRus,
> 
> I would like to loop over a medium amount of Sweave code, including both R and LaTeX chunks. Is there any way to do so? As an illustration, can I create a .tex file like this using a loop within a .Rnw file, where the "1,2,3" comes from some iteration variable in R?
> 
> ################################################
> \documentclass{article}
> \usepackage{Sweave}
> \begin{document}
> Iteration 1
> Iteration 2
> Iteration 3
> \end{document}
> ################################################

Another alternative would be to use the brew package from CRAN:

http://cran.r-project.org/web/packages/brew/index.html

While the disadvantage would be a change of syntax from Sweave to brew, 
you would gain the advantage of looping over code chunks.

brew also installs a collection of example files, one being a conversion 
of the Sweave test file to brew. Scope out the 'Examples' section from 
the brew help page.

Best,

Jeff

> 
> Right now, I do have a working but painful solution. I put the loop contents in a separate loop.Rnw file, then:
> 1. run everything before the loop through R for initialization
> 2. Sweave loop.Rnw; shell("move loop.tex loop_1.tex")
>    Sweave loop.Rnw; shell("move loop.tex loop_2.tex")
>    ...
>    Sweave loop.Rnw; shell("move loop.tex loop_n.tex")
> 3. \input all loop_i.tex files into master.Rnw and Sweave master.Rnw
> 
> This does what I need, however, it is a major pain code-wise, e.g., there appears to be no way to control the loop during execution (n must be known in advance), and I need to control all graphics using \includegraphics with the iteration counter paste()d into the filename.
> 
> An alternative may be not using Sweave and working with one giant sink() and lots of print()s, letting R just write the entire .tex file. This also appears inelegant to me.
> 
> Is there a better way to do this?
> 
> I have tried to do my homework, see below. Do I get partial credit ;-) ?
> 
> Thank you all for your time!
> Stephan
> 
> 
> #########################################
> 
> 
> I can't simply start a for loop within an R chunk and finish it in another one.
> 
> whiledo in the ifthen.sty package doesn't like Sweave at all. And of course, it would simply reuse the R chunks if it did work, without changing things between loops. For the same reason, I cannot define a \newcommand{\loopcontent}{...} with the entire loop contents and then simply write \loopcontent \loopcontent ... or \input or \include the loop content from an external file.
> 
> Of course it would be possible to not use Sweave and just use the output from the R console, but there are a couple of figures I would really like to see close to the relevant portions of the calculations.
> 
> I also thought about putting the entire loop in *one* R chunk, but then I see no way to include LaTeX chunks *within* this R chunk. I can't just sink() to the .tex file in the middle of the R chunk (as the sink() gets appended to the .tex file only after Sweave is done with it). 
> 
> I have read the Sweave manual and FAQs and the R/R Windows FAQ, I did both RSiteSearches and RSeek searches for all combinations of "Sweave" and "loop", "for", "while" I could think of.
> 
> For what it's worth, here's my sessionInfo():
> 
> R version 2.7.0 (2008-04-22) 
> i386-pc-mingw32 
> 
> locale:
> LC_COLLATE=German_Germany.1252;LC_CTYPE=German_Germany.1252;LC_MONETARY=German_Germany.1252;LC_NUMERIC=C;LC_TIME=German_Germany.1252
> 
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  tcltk     methods   base     
> 
> other attached packages:
> [1] svIDE_0.9-5
> 
> loaded via a namespace (and not attached):
> [1] svMisc_0.9-5
> 
> --
> 
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-- 
http://biostat.mc.vanderbilt.edu/JeffreyHorner