AW: [R] constructing specially ordered factor
V.Khamenia at biovision-discovery.de
Mon Oct 4 15:16:28 CEST 2004
thank you for your reply,
> does the following work in your data:
> levs <- unique.default(Names)
> factor(Names, levs[order(unique.default(Weights))])
your solution is really shorter, but has two issues to be
1. "unique.default" is applied twice, what might
be a bit expensive for strings.
2. your solution brings an implicit prerequisit on
"unique.default". Indeed, "unique.default" should
preserve the same order for output both working
with strings and with numbers. In other words,
correspondence must be kept by "unique.default".
If "unique.default" implementation uses (or will use)
lexicographic strings sorting for acceleration
then this approach fails.
More information about the R-help