[R] understanding dump.frames; typo;

Matt Shotwell Matt.Shotwell at Vanderbilt.Edu
Tue Apr 12 18:29:37 CEST 2011

When a function I have stop()s, I'd like it to return its evaluation 
frame, but not halt execution of the script. In experimenting with this, 
I became confused with dump.frames. From ?dump.frames:

      If ‘dump.frames’ is installed as the error handler, execution will
      continue even in non-interactive sessions.  See the examples for
      how to dump and then quit.

Suppose I save the following script to "dump-test.R":

cat("interactive:", interactive(), "\n")
f <- function() {
     cat("execution continues within f\n")
cat("execution continues outside of f\n")
     cat("last.dump is available\n")

 From an interactive R prompt, execution is halted at 'stop':

R> source('dump-test.R')
interactive: TRUE
Error in f() : dump-test-error

Using Rscript, execution continues depending on whether you source() the 
file with the -e flag, or pass the file as an argument.

matt at pal ~$ Rscript dump-test.R
interactive: FALSE
Error in f() : dump-test-error
execution continues outside of f
last.dump is available

matt at pal ~$ Rscript -e "source('dump-test.R')"
interactive: FALSE
Error in f() : dump-test-error
Calls: source -> eval.with.vis -> eval.with.vis -> f

It seems that interactiveness (as tested by interactive()) doesn't come 
into play, yet execution does *not* always continue. What am I missing? 
Alternative solutions are also welcome.


P.S. There is a typo in the help file: "The dumped object contain the 
call stack..." should read "The dumped object contains the call stack...".

 > sessionInfo()
R version 2.13.0 alpha (2011-03-18 r54865)
Platform: x86_64-unknown-linux-gnu (64-bit)

  [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
  [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
  [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
  [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
  [9] LC_ADDRESS=C               LC_TELEPHONE=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] tools_2.13.0

Matthew S Shotwell   Assistant Professor           School of Medicine
                      Department of Biostatistics   Vanderbilt University

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