R语言: aggragate()

对数据框格式的数据进行分组、运算和整理呈现

> ToothGrowth
    len supp dose
1   4.2   VC  0.5
2  11.5   VC  0.5
3   7.3   VC  0.5
4   5.8   VC  0.5
5   6.4   VC  0.5
6  10.0   VC  0.5
7  11.2   VC  0.5
8  11.2   VC  0.5
9   5.2   VC  0.5
10  7.0   VC  0.5
11 16.5   VC  1.0
12 16.5   VC  1.0
13 15.2   VC  1.0
14 17.3   VC  1.0
15 22.5   VC  1.0
16 17.3   VC  1.0
17 13.6   VC  1.0
18 14.5   VC  1.0
19 18.8   VC  1.0
20 15.5   VC  1.0
21 23.6   VC  2.0
22 18.5   VC  2.0
23 33.9   VC  2.0
24 25.5   VC  2.0
25 26.4   VC  2.0
26 32.5   VC  2.0
27 26.7   VC  2.0
28 21.5   VC  2.0
29 23.3   VC  2.0
30 29.5   VC  2.0
31 15.2   OJ  0.5
32 21.5   OJ  0.5
33 17.6   OJ  0.5
34  9.7   OJ  0.5
35 14.5   OJ  0.5
36 10.0   OJ  0.5
37  8.2   OJ  0.5
38  9.4   OJ  0.5
39 16.5   OJ  0.5
40  9.7   OJ  0.5
41 19.7   OJ  1.0
42 23.3   OJ  1.0
43 23.6   OJ  1.0
44 26.4   OJ  1.0
45 20.0   OJ  1.0
46 25.2   OJ  1.0
47 25.8   OJ  1.0
48 21.2   OJ  1.0
49 14.5   OJ  1.0
50 27.3   OJ  1.0
51 25.5   OJ  2.0
52 26.4   OJ  2.0
53 22.4   OJ  2.0
54 24.5   OJ  2.0
55 24.8   OJ  2.0
56 30.9   OJ  2.0
57 26.4   OJ  2.0
58 27.3   OJ  2.0
59 29.4   OJ  2.0
60 23.0   OJ  2.0

> aggregate(ToothGrowth$len,by=list(ToothGrowth$supp,ToothGrowth$dose),FUN=mean)  #先以supp再以dose对len进行分组，对相同分组内的数据进行取平均值处理；在输出时，supp在第一列，dose在第二列，len的均值在第三列
  Group.1 Group.2     x
1      OJ     0.5 13.23
2      VC     0.5  7.98
3      OJ     1.0 22.70
4      VC     1.0 16.77
5      OJ     2.0 26.06
6      VC     2.0 26.14
> aggregate(ToothGrowth$len,by=list(ToothGrowth$dose, ToothGrowth$supp),FUN=mean)
  Group.1 Group.2     x
1     0.5      OJ 13.23
2     1.0      OJ 22.70
3     2.0      OJ 26.06
4     0.5      VC  7.98
5     1.0      VC 16.77
6     2.0      VC 26.14