age occ$ vc
1  A  4.31
1  A  4.89
1  A  4.05
1  A  4.44
1  A  4.59
2  A  4.13
2  A  4.61
2  A  3.91
2  A  4.52
2  A  4.43
3  A  3.79
3  A  4.17
3  A  4.47
3  A  4.35
3  A  3.59
1  B  4.68
1  B  6.18
1  B  4.48
1  B  4.23
1  B  5.92
2  B  3.41
2  B  3.64
2  B  3.32
2  B  3.51
2  B  3.75
3  B  4.63
3  B  4.59
3  B  4.90
3  B  5.31
3  B  4.81
1  C  4.17
1  C  3.77
1  C  5.20
1  C  5.28
1  C  4.44
2  C  3.89
2  C  3.64
2  C  4.18
2  C  4.48
2  C  4.27
3  C  5.81
3  C  5.20
3  C  5.34
3  C  5.94
3  C  5.56
1  D  5.75
1  D  5.70
1  D  5.53
1  D  5.97
1  D  5.52
2  D  4.58
2  D  5.21
2  D  5.50
2  D  5.18
2  D  4.15
3  D  6.89
3  D  6.18
3  D  6.21
3  D  7.56
3  D  6.73