R 在两个变量上聚合数据框并应用函数

Question

我有一个数据框，我想聚合两个变量，在每个测量值上应用函数均值。这里是数据帧的头部：

  Subject Activity         meassureA         meassureB         meassureC       meassureD
1       1  running         0.2820216      -0.037696218       -0.13489730       -0.3282802
2       1  running         0.2558408      -0.064550029       -0.09518634       -0.2292069
3       1  walking         0.2548672       0.003814723       -0.12365809       -0.2751579
4       2  running         0.3433705      -0.014446221       -0.16737697       -0.2299235

现在，我想得到这样的东西：

  Subject Activity         meassureA         meassureB         meassureC       meassureD
1       1  running         mean(S1,A1)      mean(S1,A1)       mean(S1,A1)       mean(S1,A1)
2       1  walking         mean(S1,A2)      mean(S1,A2)       mean(S1,A2)       mean(S1,A2)
3       2  running         mean(S2,A1)      mean(S2,A1)       mean(S2,A1)       mean(S2,A1)
4       2  walking         mean(S2,A2)      mean(S2,A2)       mean(S2,A2)       mean(S2,A2)

其中测量值 A 是执行 activity 运行 (A1) 的受试者 1 (S1) 所有值的平均值。

我正在考虑使用 aggregate()，但我无法将到目前为止学到的知识应用到我的问题中。非常感谢任何帮助。

Answer 1

正如 David 在评论中提到的那样，您会这样做：

aggregate(. ~ Subject + Activity, df, mean)

或使用data.table:

data.table::setDT(df)[, lapply(.SD, mean), by = .(Subject, Activity)]

或使用dplyr:

library(dplyr)
df %>% group_by(Subject, Activity) %>% summarise_each(funs(mean))

给出：

#  Subject Activity meassureA    meassureB  meassureC  meassureD
#1       1  running 0.2689312 -0.051123123 -0.1150418 -0.2787436
#2       1  walking 0.2548672  0.003814723 -0.1236581 -0.2751579
#3       2  running 0.3433705 -0.014446221 -0.1673770 -0.2299235

R 在两个变量上聚合数据框并应用函数

R aggregate dataframe on two variables and apply function

aggregate

r