r - 只保留第一个重复的行

Question

在我的数据框中，如果字符串 Position 在第一行下方的行中多次出现，我只想保留 first 行。请看我的输出示例。我正在尝试 duplicated 函数，但我不确定如何保留第一行。

Time    Pos
2006-01-12  Position
2006-01-16  Position
2006-01-17  Position
2006-02-01  
2006-02-01  Position
2006-02-02  
2006-02-02  Position
2006-02-02  Position
2006-02-02  Position
2006-04-04  Position
2006-04-06  Position
2006-04-06  Position
2006-10-11  
2006-10-17  Position
2006-10-18  
2006-10-18  Position
2006-10-18  
2006-10-18  Position
2006-10-18  
2006-10-18  Position
2006-10-18  Position
2006-10-18  Position
2006-10-18  Position
2006-10-19  Position

输出:

Time    Pos
2006-01-12  Position
2006-02-01  
2006-02-01  Position
2006-02-02  
2006-02-02  Position
2006-10-11  
2006-10-17  Position
2006-10-18  
2006-10-18  Position
2006-10-18  
2006-10-18  Position
2006-10-18  
2006-10-18  Position

Answer 1

这是一个使用 dplyr + data.table::rleid 的解决方案:

library(dplyr)

df %>%
  mutate(ID = data.table::rleid(df$Pos)) %>%
  group_by(ID) %>%
  slice(1) %>%
  ungroup() %>%
  select(-ID)

结果:

# A tibble: 13 x 2
         Time      Pos
        <chr>    <chr>
 1 2006-01-12 Position
 2 2006-02-01         
 3 2006-02-01 Position
 4 2006-02-02         
 5 2006-02-02 Position
 6 2006-10-11         
 7 2006-10-17 Position
 8 2006-10-18         
 9 2006-10-18 Position
10 2006-10-18         
11 2006-10-18 Position
12 2006-10-18         
13 2006-10-18 Position

或 data.table 等效项:

setDT(df)[, .SD[1], by = rleid(Pos), .SDcol = c("Time", "Pos")]

结果:

    rleid       Time      Pos
 1:     1 2006-01-12 Position
 2:     2 2006-02-01         
 3:     3 2006-02-01 Position
 4:     4 2006-02-02         
 5:     5 2006-02-02 Position
 6:     6 2006-10-11         
 7:     7 2006-10-17 Position
 8:     8 2006-10-18         
 9:     9 2006-10-18 Position
10:    10 2006-10-18         
11:    11 2006-10-18 Position
12:    12 2006-10-18         
13:    13 2006-10-18 Position

数据:

df = structure(list(Time = c("2006-01-12", "2006-01-16", "2006-01-17", 
"2006-02-01", "2006-02-01", "2006-02-02", "2006-02-02", "2006-02-02", 
"2006-02-02", "2006-04-04", "2006-04-06", "2006-04-06", "2006-10-11", 
"2006-10-17", "2006-10-18", "2006-10-18", "2006-10-18", "2006-10-18", 
"2006-10-18", "2006-10-18", "2006-10-18", "2006-10-18", "2006-10-18", 
"2006-10-19"), Pos = c("Position", "Position", "Position", "", 
"Position", "", "Position", "Position", "Position", "Position", 
"Position", "Position", "", "Position", "", "Position", "", "Position", 
"", "Position", "Position", "Position", "Position", "Position"
)), .Names = c("Time", "Pos"), class = "data.frame", row.names = c(NA, 
-24L))