提取两个重复字符串之间的文本子字符串

Question

我有一个使用readtext（）创建的数据框。它具有两列：doc_id，文本。对于每一行（doc_id），我想提取两个在文本列中重复n次的字符串之间的子字符串（以我的政府部门名称）。例如：

documents <- data.frame(doc_id = c("doc_1", "doc_2"),
                        text = c("PART 1 Department of Communications \n Matters \n Blah blah blah \n PART 2 Department of Forestry \n Matters \n Blah blah blah", "PART 1 Department of Communications \n Matters \n Blah blah blah \n PART 3 Department of Health \n Matters \n Blah blah blah \n PART 5 Department of Sport \n Matters \n Blah blah"))

我想去的是：

"doc_1"  "Department of Communications, Department of Forestry"
"doc_2"  "Department of Communications, Department of Health, Department of Sport"

基本上，我想在PART和Matters之间提取字符串。我想在数据帧上使用dplyr :: rowwise操作，但不知道如何在两个重复的字符串之间提取多次。

Answer 1

我们可以使用str_match_all中的stringr并提取“ PART”和“ Matters”之间的单词。它返回一个包含两列矩阵的列表，我们从中选择第二列作为捕获组，然后使用toString将它们放在一个逗号分隔的字符串中。

out <- stringr::str_match_all(documents$text, "PART \\d+ (.*) \n Matters")
sapply(out, function(x) toString(x[, 2]))

#[1] "Department of Communications, Department of Forestry"                   
#[2] "Department of Communications, Department of Health, Department of Sport"

Answer 2

我现在想不出rowwise解决方案，但这也许也有帮助

library(dplyr)
documents %>%
  mutate(text=strsplit(as.character(text), 'PART ')) %>%
  tidyr::unnest(text) %>%
  mutate(text=trimws(sub('\\d+ (.*) Matters.*', '\\1', text))) %>%
  filter(text != '') %>%
  group_by(doc_id) %>%
  summarise(text=paste(text, collapse=', '))

它基本上在PART处分割了所有文本，然后我们可以分别处理每个元素，以从较长的字符串中切出重要的文本。稍后，我们根据doc_id将所有内容连接在一起。

Answer 3

#Import Tidyverse
library(tidyverse)

#Use helper variable name to store resuts of the extracted departments based on the parttern
Helper <- str_extract_all(string = documents$text, pattern = "Department.*\\n")

#Clean Up the columns.
Helper1 <- lapply(Helper, FUN = str_replace_all, pattern=" \\n", replacement = ", ")
documents$Departments<-str_replace(str_trim(unlist(lapply(Helper1, FUN =paste, collapse= ""))), pattern = ",$", replacement = "")

#Remove Previous column of texts
documents <- select(documents, -c("text"))

这产生