[Rd] Why is there no c.factor?

Patrick Burns pburns at pburns.seanet.com
Thu Feb 4 17:45:21 CET 2010

The argument I have in 'The R Inferno'
is that how you want to combine factors
may differ from someone else's desires.

There are lots of tricky questions:
What about ordered factors?
What if the ordered levels are different in
different objects?


On 04/02/2010 15:53, Hadley Wickham wrote:
> Hi all,
> Is there are reason that there is no c.factor method?  Analogous to
> c.Date, I'd expect something like the following to be useful:
> c.factor<- function(...) {
>    factors<- list(...)
>    levels<- unique(unlist(lapply(factors, levels)))
>    char<- unlist(lapply(factors, as.character))
>    factor(char, levels = levels)
> }
> c(factor("a"), factor("b"), factor(c("c", "b","a")), factor("d"))
> # [1] a b c b a d
> # Levels: a b c d
> Hadley

Patrick Burns
pburns at pburns.seanet.com
(home of 'The R Inferno' and 'A Guide for the Unwilling S User')

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