On Fri, 8 Jan 2010 13:25:24 +0100 Hans-Jörg Bibiko <bib...@eva.mpg.de> wrote: > Thanks for the hint! > The absolute length can make sense of course but if I need also > the largest rivers of a smaller island then this fails or it's much > more tricky to handle/select.
Not really. You could for example use 'ddply' from the 'plyr' package to get the names/IDs of the longest rivers for each country/island/... Then select the rivers with these names/IDs. -- Karl Ove Hufthammer _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
