Re: [Rd] Sweave processes \Sexpr in commented LaTeX source

From: Jean lobry <>
Date: Thu 21 Sep 2006 - 14:08:12 GMT


>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 :

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 :

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 R. Lobry            (
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

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