levels() counter-intuitif? (PR#1693)
Suppose I have a factor size with levels "small", "medium" and "large". Then, when I subset this factor:
ss<-size[size!="medium"]
to get at the extremes,
levels(ss)
.... Levels: large medium small
sure, because you didn't change the levels attribute of the factor object ss. And there is no statement in the documentation that subsetting a factor object touches the levels attribute. So why is this a bug? If I remember correctly, there was a dicussion about this issue a few month ago on this list ... Torsten
The same happens with
subset( size, size!="medium")
I understand that the resulting factor inherits the possible levels from its "parent", but I do not see in what that is useful. Intuitively, I would expect that levels(ss) return "small" and "large". For subset(), there might be an option to request inheritance of the number of levels. RenE J.V. Bertin College de France/LPPA 11, place Marcelin Berthelot 75005 Paris, France
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