如何在 tibble 列中找到最长的重复序列？答案

【问题标题】：How to find the longest duplicate sequence in a tibble column?如何在 tibble 列中找到最长的重复序列？
【发布时间】：2020-03-04 10:22:41
【问题描述】：

我更新了我的问题，因为我的输出表还需要一列。

我有以下小标题：

library(tibble)

my_tbl <- tribble(
  ~year, ~event_id, ~winner_id, 
  2011,      "A",     4322,
  2012,      "A",     4322,
  2013,      "A",     4322,
  2014,      "A",     5478,
  2015,      "A",     4322,
  2011,      "B",     4322,
  2012,      "B",     7893,
  2013,      "B",     7893,
  2014,      "B",     2365,
  2015,      "B",     3407,
  2011,      "C",     5556,
  2012,      "C",     5556,
  2013,      "C",     1238,
  2014,      "C",     2391,
  2015,      "C",     2391,
  2011,      "D",     4219,
  2012,      "D",     7623,
  2013,      "D",     8003,
  2014,      "D",     2851,
  2015,      "D",     0418
)

我想按事件 ID 找出连续最多的胜利。我正在寻找的结果如下所示：

results_summary_tbl

谢谢

【问题讨论】：

答案应该是A B C D 4 2 2 1，而不是A B C D 3 2 2 1?
啊，对不起，你的意思是最长的连续连续...

标签： r tibble run-length-encoding

【解决方案1】：

一个dplyr 选项可以是：

my_tbl %>%
 add_count(event_id, rleid = cumsum(winner_id != lag(winner_id, default = first(winner_id)))) %>%
 group_by(event_id) %>%
 summarise(most_wins_in_a_row = max(n),
           number_of_winners = n_distinct(winner_id[n == max(n)]),
           winners = paste0(unique(winner_id[n == max(n)]), collapse = ","))

  event_id most_wins_in_a_row number_of_winners winners                
  <chr>                 <int>             <int> <chr>                  
1 A                         3                 1 4322                   
2 B                         2                 1 7893                   
3 C                         2                 2 5556,2391              
4 D                         1                 5 4219,7623,8003,2851,418

【讨论】：

【解决方案2】：

在按“event_id”分组后获得最长相邻相似元素的一个选项是使用rle。它返回lengths 的list 和对应的values。通过创建一个逻辑。使用max 'lengths' 的表达式，对'values'进行子集化并获取长度

library(dplyr)
library(purrr)
my_tbl %>% 
   group_by(event_id) %>%
   summarise(rl = list(rle(winner_id)),
            most_wins_in_a_row =  map_int(rl, ~ max(.x$lengths)),
            number_of_winners = map2_int(rl, most_wins_in_a_row, 
                 ~ sum(.x$lengths == .y)), 
           winners = map2_chr(rl, most_wins_in_a_row, 
               ~ toString(.x$values[.x$lengths == .y]))) %>%
   select(-rl)
# A tibble: 4 x 4
#  event_id most_wins_in_a_row number_of_winners winners                    
#  <chr>                 <int>             <int> <chr>                      
#1 A                         3                 1 4322                       
#2 B                         2                 1 7893                       
#3 C                         2                 2 5556, 2391                 
#4 D                         1                 5 4219, 7623, 8003, 2851, 418

【讨论】：