R devel - Sep 2006 - Sweave processes \Sexpr in commented LaTeX source

Marc,
>I have a large .Rnw file and was in the process of doing some debugging.
>I had set some R chunks to 'eval=false' in the process. This
resulted in
>some R objects not being created that were in turn used in the
>subsequent \Sexpr's.
I have often the same problem, I'm using a construct like :

<<eval=F>>x <- rnorm(100)
@

I have \Sexpr{ifelse(exists("x"), length(x), "???")}
elements
in vector x.

This works well for me, and you have more control than a global
\SweaveOpts{eval.Sexpr=false} would allow, for instance :

<<TimeConsumingCodeChunk1,eval=F>>x <- rnorm(100)
...
@

I have \Sexpr{ifelse(exists("x"), length(x), "Ooops, I forgot
to evaluate TimeConsumingCodeChunk1")} elements in vector x.

Wouldn't it be enough to mention this in Sweave's FAQ ?

Best,

Jean
-- 
Jean R. Lobry            (lobry at biomserv.univ-lyon1.fr)
Laboratoire BBE-CNRS-UMR-5558, Univ. C. Bernard - LYON I,
43 Bd 11/11/1918, F-69622 VILLEURBANNE CEDEX, FRANCE
allo  : +33 472 43 27 56     fax    : +33 472 43 13 88
http://pbil.univ-lyon1.fr/members/lobry/

[shameless plug]

Jean lobry <lobry at biomserv.univ-lyon1.fr>
writes:
> <<TimeConsumingCodeChunk1,eval=F>>> x <- rnorm(100)
> ...
> @
>
> I have \Sexpr{ifelse(exists("x"), length(x), "Ooops, I
forgot
> to evaluate TimeConsumingCodeChunk1")} elements in vector x.
For the case of TimeConsumingCodeChunks, another solution is the
weaver package that caches the results of such chunks.  So you could
have:

<<TimeConsumingCodeChunk1, cache=TRUE>>x <- rnorm(100)
...
@

Then as long as the dependencies of the expressions in
TimeConsumingCodeChunk1 don't change, it won't be recomputed.

Best,

+ seth

On Thu, 2006-09-21 at 16:08 +0200, Jean lobry wrote:
> Marc,
> 
> >I have a large .Rnw file and was in the process of doing some
debugging.
> >I had set some R chunks to 'eval=false' in the process. This
resulted in
> >some R objects not being created that were in turn used in the
> >subsequent \Sexpr's.
> 
> I have often the same problem, I'm using a construct like :
> 
> <<eval=F>>> x <- rnorm(100)
> @
> 
> I have \Sexpr{ifelse(exists("x"), length(x), "???")}
elements
> in vector x.
> 
> This works well for me, and you have more control than a global
> \SweaveOpts{eval.Sexpr=false} would allow, for instance :
> 
> <<TimeConsumingCodeChunk1,eval=F>>> x <- rnorm(100)
> ...
> @
> 
> I have \Sexpr{ifelse(exists("x"), length(x), "Ooops, I
forgot
> to evaluate TimeConsumingCodeChunk1")} elements in vector x.
> 
> Wouldn't it be enough to mention this in Sweave's FAQ ?
Jean,

Thanks for your comments and approach. I will keep it in mind.

In my case, I had a large flow/org type chart that I created with
pstricks and there were quite a few Sexpr's in the chart code. All of
the Sexpr's were based upon common objects created in preceding R
chunks. I considered that it would be easier to simply treat it all as a
common block that could be commented.

Based upon Fritz' reply today, it seems that we will have an easier
solution coming.

Best regards,

Marc