r - dplyr summarise over nested group_by -
i have data frame this: date amount category 1 02.07.15 1 1 2 02.07.15 2 1 3 02.07.15 3 1 4 02.07.15 4 2 5 03.07.15 5 2 6 04.07.15 6 3 7 05.07.15 7 3 8 06.07.15 8 3 9 07.07.15 9 4 10 08.07.15 10 5 11 09.07.15 11 6 12 10.07.15 12 4 13 11.07.15 13 4 14 12.07.15 14 5 15 13.07.15 15 5 16 14.07.15 16 6 17 15.07.15 17 6 18 16.07.15 18 5 19 17.07.15 19 4 i calculate sum of amount each single day in category. attempts (see code) both not sufficient. summarise(group_by(testdata, category), sum(amount)) wrong output --> here sum calculated on each group category sum(amount) 1 1 6 2 2 9 3 3 21 4 4 53 5 5 57 6 6 44 summarise(group_by(testdata, date), s...