[R] Changing values (factors) does not change levels of that value?!
p.pagel at wzw.tum.de
Sun Nov 16 14:35:08 CET 2008
> * 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']
 A B A
Levels: A B C
 A B A
Levels: A B
Dr. Philipp Pagel
Lehrstuhl für Genomorientierte Bioinformatik
Technische Universität München
85350 Freising, Germany
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