R devel - Aug 1999 - Strange 'Unimplemented feature in rep' error (PR#254)

I have a large computation that performs various bootstrap resampling
loops over pairs of samples using lapply().
After a few seconds it stops like this
> do.summarize.effects(compute.power=T)
...
Error: Unimplemented feature in rep
> .Traceback
[[1]]
[1] "rep(no, length = length(ans))"

[[2]]
[1] "ifelse(t.howto == \"n\", boot.result,
l.meanboot.test(onew.x, onew.y, " "    samples = boot.test.samples,
expect = makezero, return.htest = T, "
[3] "    alt = \"t\"))"

[[3]]
[1] "measure.power(firstset, secondset, t.howto = t.howto, var.equal =
var.equal)"

[[4]]
[1] "FUN(X[[i]], ...)"

[[5]]
[1] "lapply(split(X, group), FUN, ...)"

[[6]]
[1] "tapply(1:nrow(dd), grouping, summarize.effects, compute.power =
compute.power)"

[[7]]
[1] "as.list(X)"

[[8]]
[1] "lapply(as.list(X), FUN, ...)"

[[9]]
[1] "sapply(tapply(1:nrow(dd), grouping, summarize.effects, compute.power =
compute.power), " "    rbind)"

[[10]]
[1] "t(sapply(tapply(1:nrow(dd), grouping, summarize.effects, compute.power
= compute.power), " "    rbind))"

[[11]]
[1] "do.summarize.effects(compute.power = T)"

My problems are the following:

1. I cannot find the line
     rep(no, length = length(ans))
   anywhere in my own code

2. The R source code of 'rep' does not contain the error message
   "unimplemented feature" (I have not checked the .Internal)

3. I've had similar strange errors before and could not find the problem
   in my own code. The problem finally went away after I renamed two
   of the groups in my data such that the factor ordering changed and
   the computations were performed in a different order...
   
4. I've also previously had the effect that my function that reads the data
   using read.table(), which is not part of the above call,
   reproducibly came up with the second column being NULL instead
   of 1451 items as the other colums. A second call to the same function
   reliably came back with the correct result. I am not sure whether
   these problems are related but I think both were not my fault.

Any suggestions where to look for the above problem?
Both my data and my computations are somewhat lengthy so the 
stepwise-stripping-down approach is cumbersome.
The new problem appeared using the same data as in (3) above, but
after some extensions to the code (none of them introducing a new
call to rep()).
The problem does also appear if I use only the small subset of the 
data used in the respective part of the computation that fails.

Thanks in advance for your help

  Lutz

Lutz Prechelt  http://wwwipd.ira.uka.de/~prechelt/   | Whenever you 
Institut f. Programmstrukturen und Datenorganisation | complicate things,
Universitaet Karlsruhe;  D-76128 Karlsruhe;  Germany | they get
(Phone: +49/721/608-4068, FAX: +49/721/608-7343)     | less
simple.
>>> Ever had negative research results?  http://wwwipd.ira.uka.de/fnr
<<<
--please do not edit the information below--

Version:
 platform = alpha-dec-osf4.0
 arch = alpha
 os = osf4.0
 system = alpha, osf4.0
 status = 
 status.rev = 0
 major = 0
 minor = 64.1
 year = 1999
 month = May
 day = 8
 language = R

Search Path:
 .GlobalEnv, Autoloads, package:base


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On Mon, 23 Aug 1999 prechelt@ira.uka.de wrote:
> I have a large computation that performs various bootstrap resampling
> loops over pairs of samples using lapply().
> After a few seconds it stops like this
> 
> > do.summarize.effects(compute.power=T)
> ...
> Error: Unimplemented feature in rep
> > .Traceback
(use traceback(): it is easier to read)
> [[1]]
> [1] "rep(no, length = length(ans))"
> 
> [[2]]
> [1] "ifelse(t.howto == \"n\", boot.result,
l.meanboot.test(onew.x, onew.y, " "    samples = boot.test.samples,
expect = makezero, return.htest = T, "
> [3] "    alt = \"t\"))"
> 
> [[3]]
> [1] "measure.power(firstset, secondset, t.howto = t.howto, var.equal =
var.equal)"
> 
> [[4]]
> [1] "FUN(X[[i]], ...)"
> 
> [[5]]
> [1] "lapply(split(X, group), FUN, ...)"
> 
> [[6]]
> [1] "tapply(1:nrow(dd), grouping, summarize.effects, compute.power =
compute.power)"
> 
> [[7]]
> [1] "as.list(X)"
> 
> [[8]]
> [1] "lapply(as.list(X), FUN, ...)"
> 
> [[9]]
> [1] "sapply(tapply(1:nrow(dd), grouping, summarize.effects,
compute.power = compute.power), " "    rbind)"
> 
> [[10]]
> [1] "t(sapply(tapply(1:nrow(dd), grouping, summarize.effects,
compute.power = compute.power), " "    rbind))"
> 
> [[11]]
> [1] "do.summarize.effects(compute.power = T)"
> 
> My problems are the following:
> 
> 1. I cannot find the line
>      rep(no, length = length(ans))
>    anywhere in my own code
Look at the line below in the traceback: it is in ifelse.
> 2. The R source code of 'rep' does not contain the error message
>    "unimplemented feature" (I have not checked the .Internal)
Look in src/main/seq.c. It means that the first arg of rep is an
unimplemented type of SEXP. It is hard to guess what: it checks that it is
a vector or list.
> 3. I've had similar strange errors before and could not find the
problem
>    in my own code. The problem finally went away after I renamed two
>    of the groups in my data such that the factor ordering changed and
>    the computations were performed in a different order...
Usually these indicate a problem with something being empty. What exactly
does l.meanboot.test return, under all possible inputs?  Your code is
trying to replicate whatever it does return (omitting NAs), and failing.

In the absence of a post-mortem debugger in R, traceback() is a very useful
tool, worth getting to grips with. I grepped the sources to find the
error message, something I resort to not infrequently.

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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