[R] puzzled by math on date-time objects

[Wacek Kusnierczyk]

Stavros Macrakis wrote:
> It does seem sensible that median and quantile would work for the
> POSIXct, Date, and other classes for which they are logically
> well-defined, but strangely enough, they do not (except for odd-length
> input).  The summary function has a special case (summary.POSIXct)
> which does the straightforward, obvious thing here.  I do not
> understand why this is not done by median and quantile themselves.
>
> Conversely, for the complex class, median and quantile do not give an
> error but instead produce meaningless results
>   

median, but not quantile, seems to fail on complex:

    median(0i)
    # error, needs numeric
    quantile(0i)
    # fine

the latter is a presumably a bug, because it doesn't follow the
documentation, ?quantile:

"
     quantile(x, ...)

Arguments:

       x: numeric vectors whose sample quantiles are wanted.  Missing
          values are ignored.
"

and complex is not numeric:

    is.numeric(0i)
    # FALSE


> since the complexes do
> not form an ordered field).

  
well, in r complexes are not comparable, but they can be sorted:

    0i < 1i
    # no go
    sort(c(0i, 1i))
    # fine

vQ