[R] Levels number of a factor object

[Thomas Petzoldt]

Laurent Houdusse schrieb:

> Hi all!
> 
>     How to retrieve the levels number of a factor object?
>     See this code:
>     groups<-gl(4,10)
>     I want to retrieve the number of levels (4) of my object "groups"
>     I tried groups.levels but this don't work

Simply try:

length(levels(groups))

Thomas P.