带特殊字符的grep [英] grep with special characters

问题描述

  s < -  c（A ，B，C *，D，E *）
 grep（*，s）
 
 [1] 1 2 3 4 5 
  

这不起作用。我可以理解，因为它是一个特殊的字符。

当我阅读这里，我决定在星号之前使用\。但是这给了我一个错误：

$ $ p $ grep（\ *，s）
错误：'\ *'是字符串中无法识别的转义符\ *


我做错了什么

解决方案

你需要两次转义特殊字符，一次为R，一次为正则表达式：

  grep（'\\ *'，s）
  

I want to find the elements that contains star character in the following vector.

s <- c("A","B","C*","D","E*")
grep("*",s)

[1] 1 2 3 4 5

This is not working. I can understand that since it is a special character.
When I read here, I decided to use "\" before star character. But that gave me an error:

grep("\*",s)
Error: '\*' is an unrecognized escape in character string starting ""\*"

What am I doing wrong?

解决方案

You need to escape special characters twice, once for R and once for the regular expression:

grep('\\*', s)

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