是否有一个R函数来查找字符向量中的regexp匹配索引? [英] Is there an R function to find the index of regexp matches in a character vector?

问题描述

我正在寻找一个R函数，该函数的作用类似于 match ，仅用于正则表达式匹配而不是相等.换句话说，如果我有一个变量 r 是正则表达式的字符向量，而变量x是一个字符向量，则我希望该函数返回与 r ，它为每个正则表达式提供与该正则表达式匹配的第一个元素的索引.请注意，我不希望正则表达式匹配的字符串中的位置.我想要与每个正则表达式匹配的 element 的索引.

I'm looking for an R function that works like match only for regular expression matching instead of equality. In other words, if I have a variable r that is a character vector of regular expressions and a variable x which is a character vector, I want the function to return a numeric vector the same length as r that gives, for each regular expression, the index of the first element that matches that regular expression. Note that I don't want the position within the string where the regular expression matches. I want the index of the element that matches each regular expression.

推荐答案

您只是在寻找 grep :

x <- c("arm","foot","lefroo", "bafoobar")
r <- c("ar","^ba","$m","foo")

获取第一个正则表达式匹配索引:

Get the first regex match index:

sapply(r, function(y) grep(y,x)[1])

 ar ^ba  $m foo 
  1   4  NA   2 

获取所有正则表达式匹配索引:

Get all regex match indexes:

sapply(r, function(y) grep(y,x))

$ar
[1] 1 4 # returns matches of ar in x

$`^ba`
[1] 4

$`$m`
integer(0)

$foo
[1] 2 4

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