ggplot2;如何在分类变量中绘制两个不同组的平均线

I have a following set of data;

我有一系列的数据;

    V1 V2  V3
 1: G1 P1 82.7
 2: G2 P1 64.6
 3: G2 P1 81.2
 4: G2 P1 95.3
 5: G1 P1 80.0
 6: G2 P1   NA
 7: G2 P1 65.0
 8: G1 P1 83.8
 9: G1 P1 88.0
10: G1 P1 66.9
11: G1 P1 56.8
12: G1 P2 65.1
13: G2 P2 57.7
14: G2 P2 60.4
15: G2 P2 18.6
16: G1 P2 41.2
17: G2 P2 47.0
18: G2 P2 37.1
19: G1 P2 18.8
20: G1 P2 47.9
21: G1 P2 40.0
22: G1 P2 54.3