[R] Package pixmap breaks try() under circumstances

[Roger Bivand]

On Wed, 23 Feb 2005, Christian Lederer wrote:

> 
> Dear R users,
> 
> in some circumstances, try() shows a strange behaviour,
> when the pixmap package is loaded.
> 
> The following piece of code works as expected, if it is
> either sourced in an interactive session or invoked via
> R CMD BATCH (the try-error is printed).
> 
> However, if i invoke R using ``R --vanilla < source.R'',
> the execution halts (without printing the try-error).
> 
> # source.R
> library(pixmap)
> x <- numeric()
> y <- numeric()
> result <- try(plot(lm(x~y)))
> print(result)
> 
> If i don't use library(pixmap), than also R --vanilla < source.R
> works as expected.
> 
> This happens with R-2.0.1 and pixmap-0.4.2 under SuSE 9.2.

But this does work as expected in your setting:

library(pixmap)
x <- numeric()
y <- numeric()
result <- try(lm(x~y))
#result <- try(plot(lm(x~y)))
print(result)
res1 <- try(plot(result))
print(res1)

The failed lm() in your version seems to be muddling plot(), and the try() 
is on the plot(), not the lm(). Without pixmap present:

> getAnywhere("plot")
A single object matching 'plot' was found
It was found in the following places
  package:graphics
  namespace:graphics
with value
 ...

With pixmap:

> getAnywhere("plot")
2 differing objects matching 'plot' were found
in the following places
  package:pixmap
  package:graphics
  namespace:graphics
Use [] to view one of them

This also works:

library(pixmap)
x <- numeric()
y <- numeric()
result <- try(plot(try(lm(x~y))))
print(result)

Hope this helps.

> 
> Christian :-(
> 
> P.S.
> The reason for preferring R --vanilla script.R over R CMD BATCH is,
> that i have to produce png images for a server and want to avoid
> the bitmap device for performance reasons.
> With R --vanilla < script.R, this is possible, using the xvnc
> virtual X server.
> 
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-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no