| nlevels {base} | R Documentation | 
Return the number of levels which its argument has.
nlevels(x)
x | 
 an object, usually a factor.  | 
This is usually applied to a factor, but other objects can have levels.
The actual factor levels (if they exist) can be obtained
with the levels function.
The length of levels(x), which is zero if
x has no levels.
nlevels(gl(3, 7)) # = 3