R help - Nov 2010 - Sweave question

It seems that Sweave is supposed to be used from Latex and R is called
during the LaTeX compilation process whenever R chunks appear. What
about the other way round? I would like to run it triggered by R. Is
this possible? I understand that this does not correspond to the idea
of literate programming since it means that there is R code running
outside the document, but for my practical approach, I would like to
use Sweave more like a report extension at the end of my already
existing R scripts that combined a number of diagrams to a pdf file.

My second question is, does Sweave create a potential performance
bottleneck when used with very big data analysis compared with when
using R directly?

Ralf

Ralf B <ralf.bierig at gmail.com> [Sat, Nov 13, 2010 at 10:03:49PM
CET]:
> It seems that Sweave is supposed to be used from Latex and R is called
> during the LaTeX compilation process whenever R chunks appear. 
This is not how it works.

In the first page of 
http://www.statistik.lmu.de/~leisch/Sweave/Sweave-Rnews-2002-3.pdf
that the file is first processed by R before it can be typeset by
LaTeX.
> What
> about the other way round? I would like to run it triggered by R. Is
> this possible? 
To my understanding this is how it's done.
> I understand that this does not correspond to the idea
> of literate programming since it means that there is R code running
> outside the document, 
You lost me here.
> but for my practical approach, I would like to
> use Sweave more like a report extension at the end of my already
> existing R scripts that combined a number of diagrams to a pdf file.
> 
> My second question is, does Sweave create a potential performance
> bottleneck when used with very big data analysis compared with when
> using R directly?
> 
Not really, because the only overhead is tangling the Sweave file.
If it is very big, you may want to process only the parts you have
changed last. The package weaver seems to come in handy then, see
http://bioconductor.org/packages/2.6/bioc/vignettes/weaver/inst/doc/weaver_howTo.pdf
-- 
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