使用R中的Grepl查找数据框列中存在的单词列表

Question

我有一个数据框 df:

df <- structure(list(page = c(12, 6, 9, 65),
text = structure(c(4L,2L, 1L, 3L), 
.Label = c("I just bought a brand new AudiA6", "Get 2 years engine replacement warranty on BMW X6", 
"Volkswagen is the parent company of BMW", "ToyotaCorolla is offering new car exchange offers"), 
class = "factor")), .Names = c("page","text"), row.names = c(NA, -4L), class = "data.frame")

另外，我有一个单词列表：

wordlist <- c("Audi", "BMW", "extended", "engine", "replacement", "Volkswagen", "company", "Toyota","exchange", "brand")

我通过取消列出文本并使用 grepl 从 wordlist 中查找是否存在于列文本中的单词。

library(data.table)
setDT(df)[, match := paste(wordlist[unlist(lapply(wordlist, function(x) grepl(x, text, ignore.case = T)))], collapse = ","), by = 1:nrow(df)]

问题是，我想找到列文本中存在的单词列表的确切单词。 使用 grepl 它还显示部分匹配的单词，例如来自文本的 AudiA6 也部分匹配到单词列表中的单词 Audi。此外，我的数据框非常大，使用 grepl 需要花费大量时间来运行代码。如果可能，请推荐任何其他方法来这样做。我想要这样的东西：

df <- structure(list(page = c(12, 6, 9, 65), 
text = structure(c(4L,2L, 1L, 3L), 
.Label = c("I just bought a brand new AudiA6", "Get 2 years engine replacement warranty on BMW X6", 
 "Volkswagen is the parent company of BMW", "ToyotaCorolla is offering new car exchange offers"),
class = "factor"), match = c("exchange", "BMW,engine,replacement", 
"brand", "BMW,Volkswagen,company")), row.names = c(NA, -4L), 
class = c("data.table", "data.frame"))

Answer 1

在为要提取的每个单词添加单词边界 (\\b) 后，您可以使用 stringr 中的 str_extract_all，以便只考虑完全匹配（并且您需要使用 "|" 折叠所有单词以表示“或”）：

sapply(stringr::str_extract_all(df$text, paste("\\b", wordlist, "\\b", sep="", collapse="|")), paste, collapse=",")
# [1] "exchange"               "engine,replacement,BMW" "brand"                  "Volkswagen,company,BMW"

如果你想把它放在你的data.table：

df[, match:=sapply(stringr::str_extract_all(text, paste("\\b", wordlist, "\\b", sep="", collapse="|")), paste, collapse=",")]
df
#   page                                              text                  match
#1:   12 ToyotaCorolla is offering new car exchange offers               exchange
#2:    6 Get 2 years engine replacement warranty on BMW X6 engine,replacement,BMW
#3:    9                  I just bought a brand new AudiA6                  brand
#4:   65           Volkswagen is the parent company of BMW Volkswagen,company,BMW