r - 确定子组索引

Question

我有一个包含组和子组的大型数据框。我想确定每个组中子组的索引，如以下数据框的OUTPUT列所示：

df <- data.frame(
  Group = factor(c("A","A","A","A","A","B","B","B","B")),
  Subgroup = factor(c("a","a","b","b","b","a","a","b","b")),
  OUTPUT = c(1,1,2,2,2,1,1,2,2)
)

我尝试了几种可能性，但都没有成功。我想使用 dplyr，但是我不确定该怎么做。以下代码返回意外结果。

require(dplyr)

df <- df %>%
  group_by(Group) %>%
  mutate(
    OUTPUT_2 = dplyr::id(Subgroup)
  )

#df
#   Group Subgroup OUTPUT_2
#  (fctr)   (fctr)    (int)
#1      A        a        8
#2      A        a        8
#3      A        b        8
#4      A        b        8
#5      A        b        8
#6      B        a        4
#7      B        a        4
#8      B        b        4
#9      B        b        4

我感觉我已经接近了，但是还没到那儿。有人可以帮忙吗？

Answer 1

我们可以在factor中使用dplyr路由

library(dplyr)
df %>% 
    group_by(Group) %>%
    mutate(OUTPUT = as.numeric(factor(Subgroup, levels= unique(Subgroup))))
#   Group Subgroup OUTPUT
#  <fctr>   <fctr>  <dbl>
#1      A        a      1
#2      A        a      1
#3      A        b      2
#4      A        b      2
#5      A        b      2
#6      B        a      1
#7      B        a      1
#8      B        b      2
#9      B        b      2

或按“组”分组后，另一个选项是带有“子组”的 match元素的 unique

df %>%
   group_by(Group) %>% 
   mutate(OUTPUT = match(Subgroup, unique(Subgroup)) )
#   Group Subgroup OUTPUT
#  <fctr>   <fctr>  <int>
#1      A        a      1
#2      A        a      1
#3      A        b      2
#4      A        b      2
#5      A        b      2
#6      B        a      1
#7      B        a      1
#8      B        b      2
#9      B        b      2