R devel - Aug 2008 - names of return value of median

Dear R-devel,

The median() function assigns a name, "NA", to its return value if the
return value is NA and the input vector has names, otherwise the names attribute
is NULL. This looks strange and inconsistent with the behavior of mean().

This inconsistency becomes a problem when median() is used inside user code that
relies on consistent naming convention.

Thanks,
Vadim
> foo <- c(x=as.numeric(NA), y=as.numeric(NA), z=as.numeric(NA))
> names(mean(foo))
NULL
> names(median(foo))
[1] NA

## no names in input
> foo <- rep(as.numeric(NA), 3)
> names(median(foo))
NULL

> version
               _
platform       i386-pc-mingw32
arch           i386
os             mingw32
system         i386, mingw32
status
major          2
minor          7.1
year           2008
month          06
day            23
svn rev        45970
language       R
version.string R version 2.7.1 (2008-06-23)
>
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>>>>> "VO" == Vadim Organovich <vogranovich at
jumptrading.com>
>>>>>     on Wed, 20 Aug 2008 12:30:38 -0500 writes:
    VO> Dear R-devel,
    VO> The median() function assigns a name, "NA", to its return
value if the return value is NA and the input vector has names, otherwise the
names attribute is NULL. This looks strange and inconsistent with the behavior
of mean().

    VO> This inconsistency becomes a problem when median() is used inside
user code that relies on consistent naming convention.

    VO> Thanks,
    VO> Vadim

    >> foo <- c(x=as.numeric(NA), y=as.numeric(NA), z=as.numeric(NA))
    >> names(mean(foo))
    VO> NULL
    >> names(median(foo))
    VO> [1] NA

    VO> ## no names in input
    >> foo <- rep(as.numeric(NA), 3)
    >> names(median(foo))
    VO> NULL

I agree that this is a slight blemish.
Note that it comes from this construct :

  > foo <- c(x=NA)
  > foo[FALSE]
  named numeric(0)
  > foo[FALSE][NA]
  <NA> 
    NA 

which seems "logical" if you ponder about it.

However, for the case of the median(), we do not return names
anyway, even in the case it might make sense,
e.g. I might expect

    median( c(a = 1, b=2, d=100))

to return  c(b = 2)
but it really simply returns (unnamed) 2.

So, I'm going to change median() to return unnamed also in these
border line cases.

Martin