如何在R中按多列分组？

library(dplyr)

df <- df %>% group_by(col1, col2)

library(dplyr)

# 创建一个示例数据框
df <- data.frame(col1 = c("A", "A", "B", "B", "C"),
                 col2 = c("X", "Y", "X", "Y", "X"),
                 value = c(1, 2, 3, 4, 5))

# 按多列分组
df <- df %>% group_by(col1, col2)

# 对分组后的数据进行操作，例如计算平均值
mean_value <- df %>% summarise(mean_value = mean(value))

# 输出结果
print(mean_value)

# A tibble: 3 x 3
# Groups:   col1 [3]
  col1  col2  mean_value
  <chr> <chr>      <dbl>
1 A     X            1  
2 A     Y            2  
3 B     X            3.5