I would like to be able to combine the numeric variables (add them) according to the name of the individual as in the example below. Thanks
DF_start
Individual X Y Z
1 A 1 10 11
2 A 2 11 12
3 A 3 12 13
4 B 4 13 14
5 B 5 14 15
6 C 6 15 16
7 C 7 16 17
8 C 8 17 18
9 C 9 18 19
DF_result
Individual X Y Z
1 A 6 33 36
2 B 9 27 29
3 C 30 66 70