>>>>> <Mark.Bravington at csiro.au>
>>>>> on Wed, 25 Aug 2010 14:06:07 +1000 writes:
> I recently moved a function 'subset.with.warning' into the
'mvbutils' package (a version not yet on CRAN). When I tried RCMD CHECK,
I got this warning:
> * checking S3 generic/method consistency ... WARNING
> subset:
> function(x, ...)
> subset.with.warning:
> function(x, cond, mess.head, mess.cond, row.info, sub)
> See section 'Generic functions and methods' of the 'Writing
R Extensions'
> manual.
> I know that S3 method arguments need to be compatible with arguments of
the generic. However, 'subset.with.warning' is deliberately not a
registered S3 method,
I think that's your real trouble ... and then your users' if you
really insist.
Short answer: "Don't do that!"
There have been a few exceptions of "100 years old" R functions
which validated this rule,
the most notable probably t() and t.test(),
and we (R core) have explicitly listed them in the code base
as "yes, looks like a method for an S3 generic, but not it
ain't!",
but have basically "forbidden" to commit more such crimes.
{Also, if you are interested: I think both t() and t.test()
pre-dated S3}
> and its USAGE section doesn't include a \method{generic}{class}
statement. I couldn't see anything in "R Extensions" that says
"don't do this", so I'm wondering:
Yes, we should add a such "don't do this" somewhere.
Can you propose a good place to put it in there?
> - should this really be a NOTE not a WARNING (or nothing at all)?
{from the above: definitely a warning, if not "worse"}....
Best regards,
Martin
Martin Maechler, ETH Zurich
> - if not, shouldn't there be a more explicit statement to the
effect that "if R decides it's a method, then it damned well is a
method, whether you think it is or not"?
> - and if so, should there also be a check for functions that look like
methods but aren't registered and declared as such?
> My preference would be for the first, FWIW. Admittedly, just because I
didn't register 'subset.with.warning' as an S3 method, that
won't stop 'subset' from trying to use it if it ever encounters an
object of class "with.warning". It's a risk that I'm happy to
take, though CRAN might not be...
> I made the warning go away by adding a '...' argument to the
end of 'subset.with.warning', but that's not pretty.
> Mark Bravington
> CSIRO
> Hobart
> Australia
>> sessionInfo()
> R version 2.11.1 Patched (2010-06-30 r52418)
> i386-pc-mingw32
> locale:
> [1] LC_COLLATE=English_Australia.1252 LC_CTYPE=English_Australia.1252
LC_MONETARY=English_Australia.1252 LC_NUMERIC=C
> [5] LC_TIME=English_Australia.1252
> attached base packages:
> [1] grDevices tools tcltk stats graphics utils methods
base
> other attached packages:
> [1] ad_1.0 chstuff_1.0 handy2_1.2 tweedie_2.0.2
statmod_1.4.1 handy_1.1 debug_1.2.3 mvbutils_2.5.2
>>
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