[R] Sweave bug? when writing figures / deleting variable in chunk

From: D G Rossiter <rossiter_at_itc.nl>
Date: Wed, 27 Jun 2007 21:06:04 -0400

I have found a quite strange (to me) behaviour in Sweave. It only occurs in the following situation:

  1. define a variable in one chunk
  2. use it within a subsequent figure-generating chunk
  3. delete it at the end of that same chunk Then the Sweave driver chokes, not finding the variable name when generating the figure


% document bug2.Rnw

sel <- 1:5


Try to sweave:

 > Sweave("bug2.Rnw")
Writing to file bug2.tex
Processing code chunks ...
1 : echo term verbatim
2 : echo term verbatim pdf
Error: no function to return from, jumping to top level Error in plot(trees[sel, ]) : error in evaluating the argument 'x' in selecting a method for function 'plot'
Error in driver$runcode(drobj, chunk, chunkopts) :

        Error in plot(trees[sel, ]) : error in evaluating the argument 'x' in selecting a method for function 'plot'

The generated .tex is complete up through the rm() but no figure is generated. The file bug2-002.pdf is incomplete (corrupt).

 > plot(trees[sel, ])
 > rm(sel)

The following ALL eliminate the problem:

0. Executing the code directly, also with ESS
1. <<fig=F>>
2. moving rm(sel) to a separate, later code chunk
3. Stangle the source and then source it
4. don't use a variable, i.e. in this case:  plot(trees[1:5,])

It seems that Sweave is executing the rm(sel) before it uses it in the trees[sel,].

Technical details: R 2.5.0, Mac OS X 10.4.10, PPC Same behaviour in stand-alone R for Mac and for R within Aquamacs using ESS

Workaround: I am putting any deletions into a later code chunk. This only has the disadvantage of making more chunks, so now that I know what's happening it's no big deal. But it's driving me crazy... am I missing something? Thanks!

D. G. Rossiter
Senior University Lecturer
Department of Earth Systems Analysis
International Institute for Geo-Information Science and Earth Observation (ITC)
Hengelosestraat 99
PO Box 6, 7500 AA Enschede, The Netherlands

Phone:	+31-(0)53 4874 499
Fax:	+31-(0)53 4874 336

mailto:rossiter--at--itc.nl, Internet: http://www.itc.nl/personal/ rossiter

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