Re: [Rd] Proposal unary - operator for factors

From: Duncan Murdoch <murdoch_at_stats.uwo.ca>
Date: Wed, 03 Feb 2010 19:49:12 -0500

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

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