Dear R-help,

Like several other subscribers, I have recently encountered a problem whereby R will execute code apparently correctly and without error, but any subsequent command will yield "Error: bad value" so that R has to be killed and restarted. We have checked this out with a few different operating systems (Windows XP/Vista and Linux) and with different versions of R. We have established the following:

1. The error occurs with versions of R from 2.5.0 onwards on all the OSs we have tried, but not with earlier versions of R. 2. The error is not reproducable between machines - identical code will fail at different points on two different machines. 3. The error is not related to contributed packages, because our code doesn't use any. The code *does*, however, use repeated calls to optim() and nlm(), and passes several arguments through a sequence of functions using "...". 4. Occasionally, we get an error relating to subset replacement instead of "Error:bad value". For example:

> x <- rnorm(10)
> x[1] <- 3
Error in x[1] <- 3 : could not find function "[<-"

5. The error behaviour changes as a result of minor modifications to print() statements in the code e.g. by inserting a line that prints the value of a well-defined variable.

I suspect this really *is* a bug (particularly since it only started happening with version 2.5.0), but I figure it would be worth giving people a chance to tell me I'm an idiot before reporting it as such. In case anybody would like to try and see the error for themselves, I have uploaded some files to http://www.homepages.ucl.ac.uk/~ucakarc/Rtest/. The file ErrorDemo.r is the main script - see the file header there for more details. Files momfit.r and elmstats.dat are also required for this example to work. I'm sorry that it isn't a very simple example, but I haven't seen a simple illustration of the problem (and I couldn't find any examples in the list archives either).

With best wishes to all,
Richard
=====================================================================
                        Richard E. Chandler
                        ^^^^^^^^^^^^^^^^^^^
Room 135, Dept of Statistical Science, University College London,
1-19 Torrington Place, London WC1E 6BT, UK
Tel: +44 (0)20 7679 1880                Fax: +44 (0)20 7383 4703

Internet: http://www.ucl.ac.uk/Stats                    (department)
          http://www.homepages.ucl.ac.uk/~ucakarc       (personal)
email:    rich...@stats.ucl.ac.uk

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