[R] levels of factor when subsetting the factor

[Afshartous, David]

All,

When I take a subset of a factor the reduced factor still maintains all
the original levels of the factor when say forming the key in a plot.
The data is correct, but the variable still "remembers" the original
levels.  See below for reproducible code.  Does anyone know how to fix
this?
cheers,
dave

fact = as.factor(c(rep("A", 3),rep("B", 3), rep("C", 3)))
new.fact = fact[1:6]
> new.fact
[1] A A A B B B
Levels: A B C    ## should only show A B