Question

我需要有关正则表达式的帮助，该正则表达式提取由下划线分隔的第三个元素。下划线的数量是可变的。我可以使用str_split来做到这一点，但是有没有办法使用str_replace获得与以下相同的结果？（期望的结果是x = AAAA, BBBB, CCCC, DDDD。如果可能，请使用()保持分组。）

library(tidyverse)
library(stringr)

d <- enframe(c("asfe_01_AAAA_fses_feee",
               "asfe_87_BBBB_fses_feee",
               "99_fesf_CCCC_feee",
               "99_fesf_DDDD"),
             name = NULL, value = "txt")

d %>%
  mutate(x = str_replace(txt, "(.+)_(.+)_(.+)_*(.*)_*(.*)", "\\3"),
         want_strsplit = str_split(txt, "_", simplify = TRUE)[, 3])

#txt                    x     want_strsplit
#  <chr>                  <chr> <chr>        
#1 asfe_01_AAAA_fses_feee feee  AAAA         
#2 asfe_87_BBBB_fses_feee feee  BBBB         
#3 99_fesf_CCCC_feee      feee  CCCC         
#4 99_fesf_DDDD           DDDD  DDDD

Answer 1

您可以再利用strsplit。

mapply(`[`, strsplit(d$txt, "_"), 3)
# [1] "AAAA" "BBBB" "CCCC" "DDDD"

整件事：

splt <- strsplit(d$txt, "_")
cbind(d, x=mapply(`[`, splt, lengths(splt)), want_strsplit=mapply(`[`, splt, 3))
#                      txt    x want_strsplit
# 1 asfe_01_AAAA_fses_feee feee          AAAA
# 2 asfe_87_BBBB_fses_feee feee          BBBB
# 3      99_fesf_CCCC_feee feee          CCCC
# 4           99_fesf_DDDD DDDD          DDDD

Answer 2

使用str_replace

> d%>%mutate(x=str_replace(txt,"^((?:[^_]*_){2})([a-zA-Z]+).*","\\2"))
# A tibble: 4 x 2
  txt                    x    
  <chr>                  <chr>
1 asfe_01_AAAA_fses_feee AAAA 
2 asfe_87_BBBB_fses_feee BBBB 
3 99_fesf_CCCC_feee      CCCC 
4 99_fesf_DDDD           DDDD

第一组捕获_的前两次出现。第二组捕获最后一组之后的所有文本。
如果还可以有数字，则可以使用[[:alnum:]]

进行概括。

d%>%mutate(x=str_replace(txt,"^((?:[^_]*_){2})([[:alnum:]]+).*","\\2"))

Answer 3

带有sub

的选项

sub("^(([^_]+_){2})([^_]+).*", "\\3", d$txt)
#[1] "AAAA" "BBBB" "CCCC" "DDDD"

Answer 4

d %>%
  mutate(x = str_replace(txt, "^([^_]+)_([^_]+)_([^_]+).*", "\\3"))

[^_]代表除_

使用stringr :: str_replace在分隔符处分割字符串

4 个答案: