patients drug  x
1         1    1  8
2         1    1  4
3         1    1  0
4         1    2 10
5         1    2  8
6         1    2  6
7         1    3  8
8         1    3  6
9         1    3  4
10        2    1 16
11        2    1 12
12        2    1  8
13        2    2  6
14        2    2  4
15        2    2  2
16        2    3 17
17        2    3 14
18        2    3 11