On Mon, 15 Dec 2003 10:08:31 +1300, you wrote:
>Hi all,
>
>I have some email addresses that I would like to sort in reverse
>lexicographic order so that addresses from the same domain will be
>grouped together. How might that be done?
I'm not sure this is what you want, but this function sorts a
character vector by last letters, then 2nd last, 3rd last, and so on:
revsort <- function(x,...) {
x[order(unlist(lapply(strsplit(x,''),
function(x) paste(rev(x),collapse=''))),...)]
}
> revsort(as.character(1:20))
[1] "10" "20" "1" "11" "2" "12" "3" "13" "4" "14" "5" "15" "6"
"16" "7"
[16] "17" "8" "18" "9" "19"
The ... args are given to order(), so na.last=FALSE and
decreasing=TRUE are possibilities.
Duncan Murdoch
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