[R] How to exclude a level from a factor
Qiong Yang
qyang at bu.edu
Tue Sep 20 19:43:49 CEST 2005
Problem solved. Thanks a lot for your replies!
> x
[1] a b c
Levels: a b c
> factor(as.character(x),exclude="c")
[1] a b <NA>
Levels: a b
"exclude=" option may not work on factors.
One has to convert the factor to character first.
Qiong
On Tue, 20 Sep 2005, Sundar Dorai-Raj wrote:
>
>
> 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
>
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