[R] How to keep attributes when dropping factor levels?

[Dieter Menne]

Heinz Tuechler <tuechler <at> gmx.at> writes:

> 
> to drop unused factor levels two ways are outlined in R-help. In both 
> cases a label attribute is lost.

Brian Ripley has posted this

http://markmail.org/message/pl2odydwzv64v3u3

Dieter