R：如何使用 stringr 提取子字符串作为输出来变异以字符串模式开头并以数字结尾的字符串列？

Question

I'm creating a small example to be put into mutate(). Not sure why this doesn't work.

> str_extract("rs1234-<b>C</b>","^rs*\\d$")
[1] NA

I'd be great if you can point to my misunderstanding of the language instead of merely providing a solution. I expect to get "rs1234".

Answer 1

The ^rs*\\d$ regex matches

• ^ - start of string
• rs* - r and zero or more occurrences of s char
• \\d - a digit
• $ - end of string.

So, your pattern matches strings like rsssss1 , r3 , etc.

You need

str_extract("rs1234-<b>C</b>", "^rs\\d+")

where ^rs\\d+ matches rs at the start of string and then one or more digits. See this regex demo .

But if I just want the substring in between "rs" and the last number. What should I do?

You would use rs.*\\d :

str_extract("rs1234-<b>C</b>", "rs.*\\d")

where rs.*\\d matches rs , then any zero or more chars other than line break chars as many as possible and then a digit.

NOTE: If you need to match line endings, too, you need to prepend the last pattern with (?s) inline DOTALL modifier.

See this regex demo .