Thank you Cedric ! To clarify I give you an example :
│ Row │ a │ b │ c │ sum │ ┝━━━━━┿━━━┿━━━┿━━━━━━┿━━━━━┥ │ 1 │ X │ 2 │ 10 │12 │ │ 2 │ Y │ 1 │ 3 │ 4 │ │ 3 │ Z │ 2 │ 5 │ 7 │ │ 4 │ X │ 1 │ 20 │ 21 │ │ 5 │ X │ 2 │ 5 │ 7 │ │ 6 │ Z │ 1 │ 8 │ 9 │ I want to obtain : │ Row │ a │ b │ c │ sum_max│ ┝━━━━━┿━━━┿━━━┿━━━━┿━━━━━━━━┥ │ 1 │ X │ 1 │20 │21 │ │ 2 │ Y │ 1 │ 3 │ 4 │ │ 3 │ Z │ 1 │ 8 │ 9 │ you can see that the lines are unchanged but filtered to obtain the sum maximum. In particular the column b contains only "1". with aggregate(df2, :a, maximum) it is not the case because I would also obtain the maximum of b (2,1,2) and c. When I have duplicates in column a (X,X,X), for example : │ Row │ a │ b │ c │sum_max│ ┝━━━━━┿━━━┿━━━┿━━━━━┿━━━━━━━┥ │ 1 │ X │ 2 │ 10 │ 12 │ │ 4 │ X │ 1 │ 20 │ 21 │ │ 5 │ X │ 2 │ 5 │ 7 │ I want to remove the rows 1 and 5 because their sum is lower than row 4 . So the result is : │ Row │ a │ b │ c │ sum_max│ ┝━━━━━┿━━━┿━━━┿━━━━┿━━━━━━━━┥ │ 4 │ X │ 1 │ 20 │ 21 │ I don't wan't b_max and c_max, only sum_max. I hope my explanation is now more clear :)
