将“填充”限制为模式的最后一次出现

Question

我有这样的数据：

df <- structure(list(line = c("001", "002", "003", "004", "005", "006", 
                              "007", "008", "009", "010", "011", "012", "013", "014"), 
                     utterance = c("((m: both hands", 
                                   "((m: both hands", 
                                   "((i: DH=1, SZ=0", "((i: DH=1, SZ=0", 
                                   "((s: Preface))", "((m: both hands", 
                                   "((m: both hands clasped", 
                                   "((m: both hands clasped", 
                                   "((s: Background))", "((m: enumerating", 
                                   "((m: enumerating", 
                                   "((s: End))", "((i: DH=1, SZ=0", "((m: relax gesture))"
                              )), row.names = c(NA, 14L), class = "data.frame")

我想创建一个新列 story 和 fill 该列，其中包含与正则表达式模式 \\(\\(s 匹配的列 utterance 中的值。但我希望fill停在与这种模式匹配的最后一个值，即((s: End))。

这个fill 命令不会停在那个模式上 - 我怎样才能让fill 停在那个模式上？

library(tidyr)
df %>%
  mutate(story = ifelse(grepl("\\(\\(s", utterance), utterance, NA)) %>%
  fill(story, .direction = "down")
   line               utterance             story
1   001         ((m: both hands              <NA>
2   002         ((m: both hands              <NA>
3   003         ((i: DH=1, SZ=0              <NA>
4   004         ((i: DH=1, SZ=0              <NA>
5   005          ((s: Preface))    ((s: Preface))
6   006         ((m: both hands    ((s: Preface))
7   007 ((m: both hands clasped    ((s: Preface))
8   008 ((m: both hands clasped    ((s: Preface))
9   009       ((s: Background)) ((s: Background))
10  010        ((m: enumerating ((s: Background))
11  011        ((m: enumerating ((s: Background))
12  012              ((s: End))        ((s: End))
13  013         ((i: DH=1, SZ=0        ((s: End))
14  014    ((m: relax gesture))        ((s: End))

希望：

   line               utterance             story
1   001         ((m: both hands              <NA>
2   002         ((m: both hands              <NA>
3   003         ((i: DH=1, SZ=0              <NA>
4   004         ((i: DH=1, SZ=0              <NA>
5   005          ((s: Preface))    ((s: Preface))
6   006         ((m: both hands    ((s: Preface))
7   007 ((m: both hands clasped    ((s: Preface))
8   008 ((m: both hands clasped    ((s: Preface))
9   009       ((s: Background)) ((s: Background))
10  010        ((m: enumerating ((s: Background))
11  011        ((m: enumerating ((s: Background))
12  012              ((s: End))        ((s: End))
13  013         ((i: DH=1, SZ=0              <NA>
14  014    ((m: relax gesture))              <NA>

Answer 1

tidyr::fill 本身不这样做，但你可以再添加一个mutate：

df %>%
  mutate(story = if_else(grepl("\\(\\(s", utterance), utterance, NA_character_)) %>%
  fill(story, .direction = "down") %>%
  mutate(story = if_else(story == last(story) & duplicated(story), NA_character_, story))
#    line               utterance             story
# 1   001         ((m: both hands              <NA>
# 2   002         ((m: both hands              <NA>
# 3   003         ((i: DH=1, SZ=0              <NA>
# 4   004         ((i: DH=1, SZ=0              <NA>
# 5   005          ((s: Preface))    ((s: Preface))
# 6   006         ((m: both hands    ((s: Preface))
# 7   007 ((m: both hands clasped    ((s: Preface))
# 8   008 ((m: both hands clasped    ((s: Preface))
# 9   009       ((s: Background)) ((s: Background))
# 10  010        ((m: enumerating ((s: Background))
# 11  011        ((m: enumerating ((s: Background))
# 12  012              ((s: End))        ((s: End))
# 13  013         ((i: DH=1, SZ=0              <NA>
# 14  014    ((m: relax gesture))              <NA>

这会查找最后一次出现的 story 并删除除第一个以外的所有内容。这假设顺序很重要，并且不假设最后一个story 必须包含文字s: End，但如果您愿意，可以相应地更新逻辑。

仅供参考，我从 ifelse 更改为 if_else，因为它是类型安全的（base::ifelse 不是）。它需要明确使用哪个 NA（有超过六种不同的变体）。

Answer 2

我们可以使用na.locf

library(dplyr)
library(zoo)
df %>%
  mutate(story = ifelse(grepl("\\(\\(s", utterance), utterance, NA), 
    ind = match("((s: End))", story),
   story = replace(story, seq_len(first(ind)), 
    zoo::na.locf0(story[seq_len(first(ind))])), ind = NULL)

-输出

 line               utterance             story
1   001         ((m: both hands              <NA>
2   002         ((m: both hands              <NA>
3   003         ((i: DH=1, SZ=0              <NA>
4   004         ((i: DH=1, SZ=0              <NA>
5   005          ((s: Preface))    ((s: Preface))
6   006         ((m: both hands    ((s: Preface))
7   007 ((m: both hands clasped    ((s: Preface))
8   008 ((m: both hands clasped    ((s: Preface))
9   009       ((s: Background)) ((s: Background))
10  010        ((m: enumerating ((s: Background))
11  011        ((m: enumerating ((s: Background))
12  012              ((s: End))        ((s: End))
13  013         ((i: DH=1, SZ=0              <NA>
14  014    ((m: relax gesture))              <NA>