我有一个data.table,如下所示:
Sim j active cost
1: 1 1 1 100
2: 1 2 1 125
3: 1 3 0 200
4: 1 4 1 250
5: 2 1 1 100
6: 2 2 0 50
7: 2 3 0 125
8: 2 4 1 200
dt <- data.table(Sim = c(1, 1, 1, 1, 2, 2, 2, 2),
j = c(1, 2, 3, 4, 1, 2, 3, 4),
active = c(1, 1, 0, 1, 1, 0, 0, 1),
cost = c(100, …