提取正则表达式匹配 [英] Extract a regular expression match

问题描述

我正在尝试从字符串中提取一个数字.

I'm trying to extract a number from a string.

然后对字符串 "aaa12xxx" 执行类似 [0-9]+ 的操作，然后得到 "12".

And do something like [0-9]+ on the string "aaa12xxx" and get "12".

我认为它会是这样的:

> grep("[0-9]+", "aaa12xxx", value=TRUE)
[1] "aaa12xxx"

然后我想...

> sub("[0-9]+", "\\1", "aaa12xxx")
[1] "aaaxxx"

但我得到了某种形式的回应:

But I got some form of response doing:

> sub("[0-9]+", "ARGH!", "aaa12xxx")
[1] "aaaARGH!xxx"

我遗漏了一个小细节.

推荐答案

使用新的 stringr 包，该包以一致的语法包装了所有现有的正则表达式，并添加了一些缺失的内容:

Use the new stringr package which wraps all the existing regular expression operates in a consistent syntax and adds a few that are missing:

library(stringr)
str_locate("aaa12xxx", "[0-9]+")
#      start end
# [1,]     4   5
str_extract("aaa12xxx", "[0-9]+")
# [1] "12"

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