[R] How to exclude a level from a factor

[Sundar Dorai-Raj]

Qiong Yang wrote:
> 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?
> 


I think you want:

x <- factor(letters[1:3])
factor(as.character(x), exclude = "c")

HTH,
--sundar