[R] How to exclude a level from a factor
Qiong Yang
qyang at bu.edu
Tue Sep 20 18:59:51 CEST 2005
Hi,
I could not use 'exlcude=' option in factor()
to exclude a level from a existing factor.
x is a factor:
> x
[1] a b c
Levels: a b c
> factor(x,exclude="c")
[1] a b c
Levels: a b c
Warning message:
NAs introduced by coercion
However, "c" is not coded as NA.
The following does not work either:
> factor(x,exclude=factor("c",levels=c("a","b","c")))
[1] a b c
Levels: a b c
What's wrong with my codes?
Thanks for any help
Qiong Yang
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