[R] Changing values (factors) does not change levels of that value?!
Weiss, Bernd
bernd.weiss at uni-koeln.de
Sun Nov 16 14:44:12 CET 2008
Philipp Pagel schrieb:
>> * when then looking at str(weblog),
>> the "-" will stay in the levels, mentioned for the variable weblog$V8
>> -> BAD!
>>
>> Is this snormal behaviour?
>
> Yes, it is. The idea is that a factor has a given set of levels
> independent of how often you find them in your data - including
> the case that a level is not observed at all. E.g. gender cn take
> levels 'male' or 'female' but you may have a sample of females.
>
>> Do I have to throw out the unwanted level by myself?
>
> Yes, and it's easy:
>
>> x <- factor(c('A','B','C','A','C'))
>> y <- x[x!='C']
>> y
> [1] A B A
> Levels: A B C
>> factor(y)
> [1] A B A
> Levels: A B
>
another solution might be
> x <- factor(c('A','B','C','A','C'))
> y <- x[x!='C']
> y
[1] A B A
Levels: A B C
> y[drop = TRUE]
[1] A B A
Levels: A B
HTH,
Bernd
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