dataframe column to 2d numpy array according to dataframe another column value count

Question

I have dataframe like df=

   S  A4  P
0   1   3  7
1   1   5  4
2   1   7  5
3   1  10  6
4   3  12  2
5   3  15  3
6   3   1  7
7   2   2  4
8   2   3  5
9