R help - Aug 2008 - problem using cat within Sweave code chunks when fig=TRUE

Hello R list

I was intending to use a cat statement within Sweave code chunks that
generate greaphs to generate a readme.txt file listing all the figures
generated with a brief caption along the lines of:

desired format of "readme.txt"
_________________________________
figure1.eps   caption for figure1
figure1.pdf   caption for figure1
figure2.eps   caption for figure2
figure2.pdf   caption for figure2
_________________________________


As an example, this block of sweave code replicates what I would like to
do in principle:


<<label=codechunk1,fig=TRUE,include=FALSE>>plot(1:10)
cat("figure1.eps caption goes here
\n",file="readme.txt",append=T)
cat("figure1.pdf caption goes here
\n",file="readme.txt",append=T)
@


<<label=codechunk2,fig=TRUE,include=FALSE>>plot(11:20)
cat("figure2.eps caption goes here
\n",file="readme.txt",append=T)
cat("figure2.pdf caption goes here
\n",file="readme.txt",append=T)
@

which I originally though would produce the desired result, however, the
cat statement appears to get executed three times producing: 

readme.txt---
figure1.eps caption goes here 
figure1.pdf caption goes here 
figure1.eps caption goes here 
figure1.pdf caption goes here 
figure1.eps caption goes here 
figure1.pdf caption goes here 
figure2.eps caption goes here 
figure2.pdf caption goes here 
figure2.eps caption goes here 
figure2.pdf caption goes here 
figure2.eps caption goes here 
figure2.pdf caption goes here 

I have figured out that any sweave code with fig=TRUE appears to be
executed multiple times (up to three), presumably to write to both eps
and pdf graphics devices (not sure what the first/last execution does
though...).  

Does anyone have any ideas about how to only execute the cat statements
the first time around so that the output looks like what I specified at
the top of this message?

Paul


Paul Rustomji
Rivers and Estuaries
CSIRO Land and Water
GPO Box 1666
Canberra ACT 2601

Hi Paul,

You could

<<label=codechunk1a,fig=TRUE,include=FALSE>>plot(1:10)
@
<<label=codechunk1b>>cat("figure1.eps caption goes here
\n",file="readme.txt",append=T)
cat("figure1.pdf caption goes here
\n",file="readme.txt",append=T)
@

You can suppress one of the three executions by setting eps=FALSE in the 
code chunk options or in the document-wide \SweaveOpts
settings.

I would also be interested what the third execution is good for.

Also, if you set both eps=FALSE and pdf=FALSE, the code chunk is not 
shown in the (.tex) output, not graphic output file is produced, but the 
chunk still seems to be executed once.

  best wishes
	Wolfgang




Paul.Rustomji a csiro.au wrote:
> Hello R list
> 
> I was intending to use a cat statement within Sweave code chunks that
> generate greaphs to generate a readme.txt file listing all the figures
> generated with a brief caption along the lines of:
> 
> desired format of "readme.txt"
> _________________________________
> figure1.eps   caption for figure1
> figure1.pdf   caption for figure1
> figure2.eps   caption for figure2
> figure2.pdf   caption for figure2
> _________________________________
> 
> 
> As an example, this block of sweave code replicates what I would like to
> do in principle:
> 
> 
> <<label=codechunk1,fig=TRUE,include=FALSE>>> plot(1:10)
> cat("figure1.eps caption goes here
\n",file="readme.txt",append=T)
> cat("figure1.pdf caption goes here
\n",file="readme.txt",append=T)
> @
> 
> 
> <<label=codechunk2,fig=TRUE,include=FALSE>>> plot(11:20)
> cat("figure2.eps caption goes here
\n",file="readme.txt",append=T)
> cat("figure2.pdf caption goes here
\n",file="readme.txt",append=T)
> @
> 
> which I originally though would produce the desired result, however, the
> cat statement appears to get executed three times producing: 
> 
> readme.txt---
> figure1.eps caption goes here 
> figure1.pdf caption goes here 
> figure1.eps caption goes here 
> figure1.pdf caption goes here 
> figure1.eps caption goes here 
> figure1.pdf caption goes here 
> figure2.eps caption goes here 
> figure2.pdf caption goes here 
> figure2.eps caption goes here 
> figure2.pdf caption goes here 
> figure2.eps caption goes here 
> figure2.pdf caption goes here 
> 
> I have figured out that any sweave code with fig=TRUE appears to be
> executed multiple times (up to three), presumably to write to both eps
> and pdf graphics devices (not sure what the first/last execution does
> though...).  
> 
> Does anyone have any ideas about how to only execute the cat statements
> the first time around so that the output looks like what I specified at
> the top of this message?
> 
> Paul
> 
> 
> Paul Rustomji
> Rivers and Estuaries
> CSIRO Land and Water
> GPO Box 1666
> Canberra ACT 2601
> 
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