我有一个这样的数据集：
> ra
quality GY TH SZ DZ FP
1 B 25.5932389 23.0215577 21.2171520 23.7548859 19.9848602
2 F 13.9567819 15.8975387 16.0363831 14.4732136 16.4207350
3 M 11.7333000 10.5075000 11.1540000 12.1292000 12.9683000
4 A 8.6439000 7.8888000 8.5094000 10.4722000 11.2059000
5 G 7.8351008 8.8121504 7.9458840 8.0838209 7.5143706
6 E 8.2900000 8.2760000 10.2717000 7.0575000 6.8747000
7 J 6.0596430 6.4356378 5.4962929 5.1445980 5.8653262
8 D 3.8608517 3.9147685 4.1381946 4.1741180 5.5412901
9 C 4.3277000 5.4838000 5.1141000 5.4004000 4.1820000
10 I 3.1710598 3.9339386 3.4053352 3.1940577 3.5347168
11 …