如何添加到 group_by_at dplyr 函数中的分组

Question

尝试使用 dplyr 将分组添加到具有现有分组的 tibble，但 group_by_at() 中的“添加”似乎不起作用。有谁知道为什么？

例子：

df <- data.frame(col1 = sample(letters,100,replace = T),
                 col2 = sample(letters,100,replace = T),
                 col3 = sample(letters,100,replace = T))

# group_by_at add doesn't work as desired:
df %>%
  group_by(col1) %>%
  group_by_at('col2', add = T) %>%
  summarise(n = n()) 

# but group_by add does work as desired:
df %>%
  group_by(col1) %>%
  group_by(col2, add = T) %>%
  summarise(n = n())

Answer 1

我们需要.add的，而不是add作为Usage中建议?group_by_atIS

group_by_at(.tbl, .vars, .funs = list(), ..., .add = FALSE, .drop = group_drops(.tbl))

df %>%
  group_by(col1) %>%
   group_by_at('col2', .add = TRUE) %>%
   summarise(n = n()) 

NOTE: After the summarise step, one of the grouping variables are removed especially the last grouping variable