Question

我在正则表达式上相当新，我试图在两个字符串之间捕获文本。但如果字符串不存在，我想捕获所有文本。

以下是一个例子：

报告＃1：观察：猫正在伸展。结论：这只猫很灵活。

我可以使用以下代码捕获＆＃34; Observations＆＃34;之间的文本。和＆＃34; 结论＆＃34;：

(?:(?i)observations)(.*)(?:(?i)conclusions)

但如果另一个文字写道：

报告＃1：观察：猫正在伸展。这只猫很灵活。

我想在＆＃34; 观察＆＃34;之后捕捉所有内容。

或者如果起始字符串＆＃34; 观察＆＃34;不存在：

报告＃1：猫正在伸展。结论：这只猫很灵活。

我想从开头到结尾字符串捕获＆＃34; 结论＆＃34;。

我猜有条件的正则表达式可能有帮助吗？

谢谢！

Answer 1

执行此操作的方法是使用两个正则表达式：

reports = c(
"Report #1: Observations: A cat is stretching. Conclusions: This cat is flexible.", 
"Report #1: Observations: A cat is stretching. This cat is flexible.")

reports = sub(".*Observations:\\s*", "", reports)
reports = sub("\\s*Conclusions:.*", "", reports)

reports
[1] "A cat is stretching."                      
[2] "A cat is stretching. This cat is flexible."

Answer 2

单行：

ex <- c(
  "Report #1: Observations: A cat is stretching. Conclusions: This cat is flexible.",
  "Report #1: Observations: A cat is stretching. This cat is flexible.",
  "Report #1: A cat is stretching. Conclusions: This cat is flexible."
)

gsub("(^.*observations|conclusions.*$)", "", ex, ignore.case = TRUE)
# [1] ": A cat is stretching. "                     
# [2] ": A cat is stretching. This cat is flexible."
# [3] "Report #1: A cat is stretching. "

您可能需要边界或在单词之前/之后作为G5W建议空格。字边界看起来像这样，给出示例文本的输出相同：

gsub("(^.*\\bobservations\\b|\\bconclusions\\b.*$)", "", ex, ignore.case = TRUE)

正则表达式 - 在匹配之间捕获文本，如果不匹配，则捕获所有

2 个答案: