如何找到R数据帧的分组汇总统计信息？
为了比较不同的组，我们需要每个组的摘要统计信息。它有助于我们观察两组之间的差异。摘要统计信息提供最小值，第一四分位数，中位数，第三四分位数和最大值。因此，我们可以比较每个组的这些值。要找到R数据帧的逐组汇总统计信息，我们可以使用tapply函数。
示例
请看以下数据帧-
> set.seed(99)
> x1<-sample(1:100,50,replace=TRUE)
> x2<-rep(c("G1","G2","G3","G4","G5"),times=10)
> df<-data.frame(x1,x2)
> head(df,20)
x1 x2
1 48 G1
2 33 G2
3 44 G3
4 22 G4
5 99 G5
6 62 G1
7 98 G2
8 32 G3
9 13 G4
10 20 G5
11 100 G1
12 31 G2
13 68 G3
14 9 G4
15 82 G5
16 88 G1
17 30 G2
18 86 G3
19 84 G4
20 32 G5查找每个组的x1的摘要统计量-
> tapply(df$x1, df$x2, summary) $G1 Min. 1st Qu. Median Mean 3rd Qu. Max. 14.0 55.0 72.0 67.8 86.5 100.0 $G2 Min. 1st Qu. Median Mean 3rd Qu. Max. 4.0 31.5 60.5 52.4 69.5 98.0 $G3 Min. 1st Qu. Median Mean 3rd Qu. Max. 14.0 33.5 41.0 46.9 64.5 86.0 $G4 Min. 1st Qu. Median Mean 3rd Qu. Max. 9.00 23.75 53.00 53.30 82.75 97.00 $G5 Min. 1st Qu. Median Mean 3rd Qu. Max. 7.00 31.25 32.00 42.40 44.75 99.00
让我们再看一个例子-
> y1<-rep(c(letters[1:5]),times=5) > y2<-rep(c(14,25,13,12,41,52,44,28,17,30),times=c(2,5,3,3,1,5,1,2,2,1)) > df_y<-data.frame(y1,y2) > head(df_y,20) y1 y2 1 a 14 2 b 14 3 c 25 4 d 25 5 e 25 6 a 25 7 b 25 8 c 13 9 d 13 10 e 13 11 a 12 12 b 12 13 c 12 14 d 41 15 e 52 16 a 52 17 b 52 18 c 52 19 d 52 20 e 44 > tapply(df_y$y2, df_y$y1, summary) $a Min. 1st Qu. Median Mean 3rd Qu. Max. 12.0 14.0 25.0 26.2 28.0 52.0 $b Min. 1st Qu. Median Mean 3rd Qu. Max. 12.0 14.0 25.0 26.2 28.0 52.0 $c Min. 1st Qu. Median Mean 3rd Qu. Max. 12.0 13.0 17.0 23.8 25.0 52.0 $d Min. 1st Qu. Median Mean 3rd Qu. Max. 13.0 17.0 25.0 29.6 41.0 52.0 $e Min. 1st Qu. Median Mean 3rd Qu. Max. 13.0 25.0 30.0 32.8 44.0 52.0