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)
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