只获得R中匹配的字符串部分

Question

R中是否有与regexp匹配的函数并仅返回匹配的部分？有点像grep -o,所以:

> ogrep('.b.',c('abc','1b2b3b4'))
[[1]]
[1] abc

[[2]]
[1] 1b2 3b4

Answer 1

试试stringr:

library(stringr)
str_extract_all(c('abc','1b2b3b4'), '.b.')
# [[1]]
# [1] "abc"
# 
# [[2]]
# [1] "1b2" "3b4"

Answer 2

你应该给Gabor Grothendieck写一下gsubfn包的支票:

 require(gsubfn)
#Loading required package: gsubfn
 strapply(c('abc','1b2b3b4'), ".b.", I)

#Loading required package: tcltk
#Loading Tcl/Tk interface ... done
[[1]]
[1] "abc"

[[2]]
[1] "1b2" "3b4"

这只是将身份函数I应用于模式的匹配.

Answer 3

我需要将gregexpr和substring结合起来,我估计:

> s = c('abc','1b2b3b4')
> m = gregexpr('.b.',s)
> substring(s[1],m[[1]],m[[1]]+attr(m[[1]],'match.length')-1)
[1] "abc"
> substring(s[2],m[[2]],m[[2]]+attr(m[[2]],'match.length')-1)
[1] "1b2" "3b4"

返回的列表'm'具有匹配的开始和长度.循环s以获取所有子串.

Answer 4

我简直不敢相信regmatches!

x <- c('abc','1b2b3b4')
regmatches(x, gregexpr('.b.', x))

# [[1]]
# [1] "abc"

# [[2]]
# [1] "1b2" "3b4"

这让我很奇怪,regmatches两年半前不存在？