R help - Dec 2010 - How does Sweave write to a file?

Hello.

I need that Sweave writes R output to a file. To do it, I put the following into
the foo.Rnw file:


\documentclass{article}
\usepackage{Sweave}
\begin{document}

...

<<echo=F>>x <- rnorm(100)
y <- rnorm(100)
sink("foo.txt")
summary(lm(y~x))
sink()
@

...

\end{document}


When I run:

R CMD Sweave foo.Rnw

R responses:

Warning message:
In sink() : no sink to remove, 

and It doesn't work. Somebody knows how I can fix it?

Thanks,

Arnau.



------------------------------------------------------------
Arnau Mir Torres
Edifici A. Turmeda
Campus UIB
Ctra. Valldemossa, km. 7,5
07122 Palma de Mca.
tel: (+34) 971172987
fax: (+34) 971173003
email: arnau.mir at uib.es
URL: http://dmi.uib.es/~arnau

On 09/12/2010 2:07 PM, Arnau Mir Torres wrote:
> Hello.
>
> I need that Sweave writes R output to a file. To do it, I put the following
into the foo.Rnw file:
>
>
> \documentclass{article}
> \usepackage{Sweave}
> \begin{document}
>
> ...
>
> <<echo=F>>> x<- rnorm(100)
> y<- rnorm(100)
> sink("foo.txt")
> summary(lm(y~x))
> sink()
> @
>
> ...
>
> \end{document}
>
>
> When I run:
>
> R CMD Sweave foo.Rnw
>
> R responses:
>
> Warning message:
> In sink() : no sink to remove,
>
> and It doesn't work. Somebody knows how I can fix it?

The problem is that Sweave executes each statement wrapped within sink( 
con ); statement; sink().  You need to avoid using sink() as a separate 
statement.  One way would be to put the lines

sink("foo.txt")
summary(lm(y~x))
sink()

into a block using braces {}; Sweave would wrap the whole function call, not the
individual lines.  That's essentially what
capture.output() does, so this should work:

writeLines( capture.output( summary(lm(y~x)) ), "foo.txt")

You can probably do it in other ways too.

Duncan Murdoch