Hi, I have the following two dataframes (Df1 and Df2): Df1 has a layout like ID Location Var1 Var2 Var3 . Var20 A Loc2 1 1 1 . 1 A Loc1 0 1 0 . 1 B Loc1 0 0 0 . 0 A Loc3 1 0 1 . 0 C Loc3 1 0 1 . 0 B Loc2 0 0 0 . 1 D . .. Df2 has a layout like ID Var1 Var2 Var3 .. Var20 A 0.2 0.3 0.2 .... 0.15 B 0.1 0.1 0.1 . 0.1 C 0 0 0 . 0.50 D . . And I like to have the following result ID Location Var1 Var2 Var3 . Var20 A Loc2 0.2 0.3 0.2 . 0.15 A Loc1 0 0.3 0 . 0.15 B Loc1 0 0 0 . 0 A Loc3 0.2 0 0.2 . 0 C Loc3 0 0 0 . 0 B Loc2 0 0 0 . 0.1 D . .. Is this easy doable in R? I''ve tried to figure it out with mapply but without result. Thanks for helping me out. Bert [[alternative HTML version deleted]]