[Rd] Proposal unary - operator for factors

[Duncan Murdoch]

On 03/02/2010 7:20 PM, Hadley Wickham wrote:
>>> Currently, for numeric a you can do either
>>>   order(-a)
>>> or
>>>   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. :-)

Duncan Murdoch