R語言：group_by, summarise, arrange, slice

生成數據：

library(dplyr)
set.seed(1)
df <- expand.grid(list(A = 1:5, B = 1:5, C = 1:5))
df$value <- runif(nrow(df))

情況 1：group_by + summarise

df %>% group_by(A, B) %>% summarise(max = max(value))

情況 2：group_by + arrange

result <- df %>% group_by(A, B) %>% filter(value == max(value)) %>% arrange(A,B,C)

情況 3：group_by + top_n

df %>% group_by(A, B) %>% top_n(n=1)

情況 4：group_by + slice

df %>% group_by(A,B) %>% slice(which.max(value))