根据订单删除重复项 [英] Remove duplicates based on order

问题描述

在R中，我希望删除每个a之后的前两个b和c之后的所有实例(请注意编号). 我有以下内容:

In R, I'm looking to remove any instances after the first two b and c after each a (please note the numbering). I've got the following:

1   a
2   b
3   c
4   a
5   b
6   c
7   a
8   b
9   c
10  b
11  c
12  a
13  b
14  c
15  c

我希望将其减少为:

1   a
2   b
3   c
4   a
5   b
6   c
7   a
8   b
9   c
12  a
13  b
14  c

如果可能，我正在尝试在dplyr管道中执行此操作. 有什么想法吗?

I'm trying to do this within a dplyr pipe if possible. Any ideas?

推荐答案

一种可能的解决方案:

df = read.table(text="1   a
                2   b
                3   c
                4   a
                5   b
                6   c
                7   a
                8   b
                9   c
                10  b
                11  c
                12  a
                13  b
                14  c
                15  c",header=F)

library(dplyr)
df %>% mutate(x=cumsum(V2=='a')) %>%
  group_by(x) %>% 
  filter(!duplicated(V2)) %>% 
  ungroup() %>%
  select(-x)

输出:

# A tibble: 12 x 2
      V1     V2
   <int> <fctr>
 1     1      a
 2     2      b
 3     3      c
 4     4      a
 5     5      b
 6     6      c
 7     7      a
 8     8      b
 9     9      c
10    12      a
11    13      b
12    14      c

请注意，这每次遇到a后都会删除所有重复的元素.如果只想删除重复的b和c，请考虑:filter(!(duplicated(V2) & (V2=='b' | V2=='c')))

Note that this removes all duplicated elements every time after an a is encountered. If you only want to remove duplicated b's and c's, consider : filter(!(duplicated(V2) & (V2=='b' | V2=='c')))

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