[R] Indexing on a variable that is a factor

[Uwe Ligges]

Farrel Buchinsky wrote:
> It is easy to index on numeric variables.
> How does one index on a variable that is a factor?
> 


Same as for numeric objects. Example:

R> x <- factor(c("A", "B"))
R> x
[1] A B
Levels: A B

R> x[1]
[1] A
Levels: A B