[Rd] Proposal unary - operator for factors
Prof Brian Ripley
ripley at stats.ox.ac.uk
Thu Feb 4 05:34:18 CET 2010
On Wed, 3 Feb 2010, Duncan Murdoch wrote:
> On 03/02/2010 7:20 PM, Hadley Wickham wrote:
>>>> Currently, for numeric a you can do either
>>>> order(a, decreasing=FALSE)
>>>> For nonnumeric types like POSIXct and factors only
>>>> the latter works.
>>>> Under my proposal your
>>>> order(a, -b, c, d)
>>>> would be
>>>> order(a, b, c, d, decreasing=c(FALSE,TRUE,FALSE,TRUE))
>>>> and it would work for any ordably class without modifications
>>>> to any classes.
>>> Why not use
>>> order(a, -xtfrm(b), c, -xtfrm(d))
>> That's a good suggestion. You could make it even easier to read with
>> desc <- function(x) -xtfrm(x)
>> order(a, desc(b), c, desc(d))
>> Could you remind me what xtfrm stands for?
> No, I don't think I ever worked it out. :-)
The same logic as strxfrm.
> Duncan Murdoch
> R-devel at r-project.org mailing list
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)
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