Bug in Sweave? -- scoping problem? (PR#8615)
Berwin A Turlach wrote:
G'day Duncan,
"DM" == murdoch <murdoch at stats.uwo.ca> writes:
DM> I have found a strange scoping problem in Sweave. [...]
DM> The strange thing is that while the value in partytotal is
DM> output correctly as [...]
DM> but the dotchart contains the wrong values: it shows sorted
DM> values, but not sorted names, [...]
No bug, but a feature. :)
(But then, a well known software producer seems to use `feature' as a
euphemism for `bug', so perhaps I shouldn't call it a feature.)
There was recently a discussion on r-help (?) about Sweave producing
different output in the text and plot when random numbers were
generated, and it seems as if you have run into the same trap:
Code in chunks that produce pictures is executed several times.
First, to produce the output in the text. And then once more
for *each* format in which the figure has to be produced. I.e.,
if you want a PDF and a PostScript version of the figure, the
code is executed a total of three times.
Thanks, that's what caught me. Is that a quote from the discussion, or from the docs somewhere? It makes sense in hindsight, but it's not obvious ahead of time, so it should be stated fairly prominently in the docs. Duncan Murdoch
All instances of this feature reported so far involved commands that
produced random numbers and the poster was surprised that the output
in the text and the figures differed (and that the two figures were
different).
In your case the first execution of the code assigns the names to
partytotal, sorts partytotal and produces the data. On the next
execution, when the picture is produced, partytotal is already sorted
but you reassign the names. Then the partytotal is sorted again and
the plot is produced. But that re-assigning of names lead to the
disconnect between values and names.
Hope this helps.
Cheers,
Berwin
========================== Full address ============================
Berwin A Turlach Tel.: +61 (8) 6488 3338 (secr)
School of Mathematics and Statistics +61 (8) 6488 3383 (self)
The University of Western Australia FAX : +61 (8) 6488 1028
35 Stirling Highway
Crawley WA 6009 e-mail: berwin at maths.uwa.edu.au
Australia http://www.maths.uwa.edu.au/~berwin