sapply(Date, is.numeric)
On Wed, 30 Jul 2008, Martin Maechler wrote:
"RobMcG" == McGehee, Robert <Robert.McGehee at geodecapital.com>
on Tue, 29 Jul 2008 15:40:37 -0400 writes:
RobMcG> FYI, RobMcG> I've tried posting the below message twice to the bug tracking system, [....... r-bugs problems discussed in a separate thread ....] RobMcG> R-developers, RobMcG> The results below are inconsistent. From the documentation for RobMcG> is.numeric, I expect FALSE in both cases.
>> x <- data.frame(dt=Sys.Date()) >> is.numeric(x$dt)
RobMcG> [1] FALSE
>> sapply(x, is.numeric)
RobMcG> dt RobMcG> TRUE RobMcG> ## Yet, sapply seems aware of the Date class
>> sapply(x, class)
RobMcG> dt RobMcG> "Date" Yes, thanks a lot, Robert, for the report. That *is* a bug somewhere in the .Internal(lapply(...)) C code, when S3 dispatch of primitive functions should happen.
The bug is in do_is, which uses CHAR(PRINTNAME(CAR(call))), and when
called from lapply that gives "FUN" not "is.numeric". The root cause is
the following comment
FUN = CADR(args); /* must be unevaluated for use in e.g. bquote */
and hence that the function in the *call* passed to do_is can be
unevaluated.
Here's an R scriptlet exposing a 2nd example ### lapply(list, FUN) ### ------------------ seems to sometimes fail for ### .Primitive S3-generic functions (ds <- seq(from=Sys.Date(), by=1, length=4)) ##[1] "2008-07-30" "2008-07-31" "2008-08-01" "2008-08-02" ll <- list(d=ds) lapply(list(d=ds), round) ## -> Error in lapply(list(d = ds), round) : dispatch error
And that's a separate issue, in DispatchGroup which states that arguments have been evaluated (true) but the 'call' from lapply gives the unevaluated arguments and so there is a mismatch. I'm testing fixes for both.
## or -- related to bug report by Robert McGehee on R-devel, on 2008-07-29: sapply(list(d=ds), is.numeric) ## TRUE ## in spite of is.numeric(`[[`(ll,1)) ## FALSE , because of is.numeric.date ## or round(`[[`(ll,1)) ## [1] "2008-07-30" "2008-07-31" "2008-08-01" "2008-08-02" ##----------------------------- But I'm currently too much tied up with other duties, to find and test bug-fix. Martin Maechler, ETH Zurich and R-Core Team
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Brian D. Ripley, ripley at 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 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595