[R-sig-eco] 'grouping' grouping variable

[Jakub Szymkowiak]

Thanks for every comments and ideas!

Robera - woodland and meadows were only an example. I have also variables 
describing e.g. area of rye, wheat, barley cultivation, but I agree - all my 
variables describe habitat use in every region.
I have also a data about birds (4 species) - in every region, birds were 
countend on study plots (1km squares). The number of study plots vary 
between regions.


Cheers,
Jakub