On 28/03/2009 4:57 PM, Stavros Macrakis wrote:
On Sat, Mar 28, 2009 at 7:53 AM, Duncan Murdoch <murd...@stats.uwo.ca> wrote:
...More generally, the xtfrm() function converts a vector into a numeric one
that sorts in the same order. ...
Thanks, I learn a lot just by reading the answers to other people's
questions on this list.
Some followup questions:
1) Where does the name 'xtfrm' come from?
I don't know.
2) Why isn't xtfrm of a numeric vector the identity function?
"Because the implementation does that". It's a one liner:
xtfrm.default <- function (x)
as.vector(rank(x, ties.method = "min", na.last = "keep"))
The identity function would probably be faster, but why optimize cases
that are never needed? A better optimization would be just to use
order(x), not order(xtfrm(x)).
Duncan Murdoch
3) Similarly, why isn't xtfrm of a logical vector just as.integer of
it? (as it is for factors)
4) Why is xtfrm(c(2,3,2)) => c(1,3,1) and not c(1,2,1) or for that
matter c(2,3,2) (see point 2)?
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