下一个"specific"观察向后进行（NOCB）

Question

这是我的数据框：

library(zoo)
library(dplyr)

df <- data.frame(
  id = rep(1:4, each = 4), 
  status = c(
    NA, "a", "c", "a", 
    NA, "c", "c", "c",
    NA, NA, "a", "c",
    NA, NA, "c", "c"),
  otherVar = letters[1:16],
  stringsAsFactors = FALSE)

对于变量状态，我希望下一个观察在组 (id) 内向后进行。

df %>% group_by(id) %>% na.locf(fromLast = TRUE) %>% ungroup

但是，我只希望我的 "c" 的倒退，而不是 "a" 的倒退。

来自变量状态：

NA "a" "c" "a" NA "c" "c" "c" NA NA "a" "c" NA NA "c" "c"

我想得到：

NA "a" "c" "a" "c" "c" "c" "c" NA NA "a" "c" "c" "c" "c" "c"

分别为：

data.frame(
  id = rep(1:4, each = 4), 
  status = c(
    NA, "a", "c", "a", 
    "c", "c", "c", "c",
    NA, NA, "a", "c",
    "c", "c", "c", "c"),
  otherVar = letters[1:16],
  stringsAsFactors = FALSE)

有办法吗？

Answer 1

使用 tidyr:fill 的解决方案基于创建 dummyStatus 列。 fill dummyStatus 使用 .direction = "up"。现在使用此 dummyStatus 在实际 status 列中填充 NA 值，然后验证检查以下值应为 c.

library(dplyr)
library(tidyr)
df %>% group_by(id) %>%
    mutate(dummyStatus = status) %>%
    fill(dummyStatus, .direction = "up" ) %>%
    mutate(status = ifelse(is.na(status) & lead(dummyStatus)=="c","c",status)) %>%
    select(-dummyStatus) %>% as.data.frame()

  #    id status otherVar
  # 1   1   <NA>        a
  # 2   1      a        b
  # 3   1      c        c
  # 4   1      a        d
  # 5   2      c        e
  # 6   2      c        f
  # 7   2      c        g
  # 8   2      c        h
  # 9   3   <NA>        i
  # 10  3   <NA>        j
  # 11  3      a        k
  # 12  3      c        l
  # 13  4      c        m
  # 14  4      c        n
  # 15  4      c        o
  # 16  4      c        p

数据：

df <- data.frame(
  id = rep(1:4, each = 4), 
  status = c(
    NA, "a", "c", "a", 
    NA, "c", "c", "c",
    NA, NA, "a", "c",
    NA, NA, "c", "c"),
  otherVar = letters[1:16],
  stringsAsFactors = FALSE)

Answer 2

应用 na.locf0 后，检查每个 NA 的位置，如果现在是 a，则将其重置回 NA。如果你想覆盖 status 然后用 status = if_else(is.na(status) & status2 == "a", NA_character_, status2), status2 = NULL) %>%

替换第二行 status2=

library(dplyr)
library(zoo)

df %>% 
  group_by(id) %>% 
  mutate(status2 = na.locf0(status, fromLast = TRUE),
         status2 = if_else(is.na(status) & status2 == "a", NA_character_, status2)) %>%
  ungroup

给予：

# A tibble: 16 x 4
      id status otherVar status2
   <int> <chr>  <chr>    <chr>  
 1     1 <NA>   a        <NA>   
 2     1 a      b        a      
 3     1 c      c        c      
 4     1 a      d        a      
 5     2 <NA>   e        c      
 6     2 c      f        c      
 7     2 c      g        c      
 8     2 c      h        c      
 9     3 <NA>   i        <NA>   
10     3 <NA>   j        <NA>   
11     3 a      k        a      
12     3 c      l        c      
13     4 <NA>   m        c      
14     4 <NA>   n        c      
15     4 c      o        c      
16     4 c      p        c

下一个"specific"观察向后进行（NOCB）

Next "specific" observation carried backward (NOCB)

r

dplyr

locf