如何使用 dplyr 查找特定列中哪些组具有相同的值？

Question

我有一个包含字母和数字的表格：

xx <- tibble (letter = c (rep ("a", 3), rep ("b", 3), rep ("c", 3)),
              number = c (1, 2, 3, 1, 2, 3, 4, 5, 6))

我想首先按“字母”对数据进行分组，然后检查数字列中是否有两个具有相同值的组。这些将是“字母”列中带有字母“a”和“b”的组。

结果看起来像这样

xx <- tibble (letter = c (rep ("a", 3), rep ("b", 3), rep ("c", 3)),
              number = c (1, 2, 3, 1, 2, 3, 4, 5, 6),
              duplicated = c (rep (TRUE, 6), rep (FALSE, 3)) )

有没有办法在 dplyr 中优雅地做到这一点？

Answer 1

您可以尝试：

xx %>%
  distinct() %>%
  group_by(number) %>%
  mutate(n = n()) %>%
  mutate(duplicated = ifelse(n>1, TRUE, FALSE)) %>%
  select(-n)

      letter number duplicated
      <chr>   <dbl> <lgl>     
    1 a           1 TRUE      
    2 a           2 TRUE      
    3 a           3 TRUE      
    4 b           1 TRUE      
    5 b           2 TRUE      
    6 b           3 TRUE      
    7 c           4 FALSE     
    8 c           5 FALSE     
    9 c           6 FALSE 

distinct是因为如果组内有一些重复的内容，

xx <- tibble (letter = c (rep ("a", 4), rep ("b", 3), rep ("c", 3)),
              number = c (1,1, 2, 3, 1, 2, 3, 4, 4, 6))
   letter number
   <chr>   <dbl>
 1 a           1
 2 a           1
 3 a           2
 4 a           3
 5 b           1
 6 b           2
 7 b           3
 8 c           4
 9 c           4
10 c           6
    xxx <- xx %>%
      distinct() %>%
      group_by(number) %>%
      mutate(n = n()) %>%
      mutate(duplicated = ifelse(n>1, TRUE, FALSE)) %>%
      select(-n)

    xx %>% 
      full_join(xxx, by = c("letter", "number"))

   letter number duplicated
   <chr>   <dbl> <lgl>     
 1 a           1 TRUE      
 2 a           1 TRUE      
 3 a           2 TRUE      
 4 a           3 TRUE      
 5 b           1 TRUE      
 6 b           2 TRUE      
 7 b           3 TRUE      
 8 c           4 FALSE     
 9 c           4 FALSE     
10 c           6 FALSE  

感谢@LMc

xxx <- xx %>%
  distinct() %>%
  add_count(number) %>%
  mutate(duplicated = n> 1) %>%
  select(-n)
xxx
xx %>% 
  full_join(xxx, by = c("letter", "number"))