Hi Ivan, thanks for your replay! but the problem is there that the dataframe has 20000 rows and ca. 2000 groups, but i dont have the column with the groupnames, because the groups are depending on 2 onother columns ... any other idea or i didnt understand waht are you posted ... :( -- View this message in context: http://r.789695.n4.nabble.com/group-by-in-data-frame-tp3324240p3324327.html Sent from the R help mailing list archive at Nabble.com.
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