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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