提取两个不同模式之间的部分字符串 [英] Extract part of string between two different patterns

问题描述

我尝试使用 stringr 包来提取字符串的一部分，它位于两个特定模式之间.

I try to use stringr package to extract part of a string, which is between two particular patterns.

例如，我有:

my.string <- "nanaqwertybaba"
left.border  <- "nana"
right.border <- "baba"

并通过使用 str_extract(string, pattern) 函数(其中模式是由 POSIX 正则表达式定义)我想收到:

and by the use of str_extract(string, pattern) function (where pattern is defined by a POSIX regular expression) I would like to receive:

"qwerty"

来自 Google 的解决方案无效.

Solutions from Google did not work.

推荐答案

我不知道 stringr 提供的函数是否以及如何实现，但您也可以使用 base regexpr 和 substring:

I do not know whether and how this is possible with functions provided by stringr but you can also use base regexpr and substring:

pattern <- paste0("(?<=", left.border, ")[a-z]+(?=", right.border, ")")
# "(?<=nana)[a-z]+(?=baba)"

rx <- regexpr(pattern, text=my.string, perl=TRUE)
# [1] 5
# attr(,"match.length")
# [1] 6

substring(my.string, rx, rx+attr(rx, "match.length")-1)
# [1] "qwerty"

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