G'day Petr,
On Mon, 25 May 2009 09:04:14 +0200
Petr Savicky <savi...@cs.cas.cz> wrote:
> The first formulation "Be careful to compare ... levels in the same
> order" may be just a warning against a potential problem if the
> levels have different order, however this is not clear.
Well, the first statement is a remark on comparison in general while
the second statement is specific to "comparison operators and generic
methods". There are other ways of comparing objects; note:
R> f1 <- factor(c("a", "b", "c", "c", "b", "a"), levels=c("a", "b", "c"))
R> f2 <- factor(c("a", "b", "c", "c", "b", "a"), levels=c("c", "b", "a"))
R> f1==f2
[1] TRUE TRUE TRUE TRUE TRUE TRUE
R> identical(f1,f2)
[1] FALSE
R> all.equal(f1,f2)
[1] "Attributes: < Component 2: 2 string mismatches >"
Just my 2c.
Cheers,
Berwin
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