如何使用 stringr 将括号内最后出现的字符串与列字符串提取到另一列中？答案

【问题标题】：How do I extract the last occurring string within a parentheses with a column string into another column using stringr?如何使用 stringr 将括号内最后出现的字符串与列字符串提取到另一列中？
【发布时间】：2020-04-28 18:14:56
【问题描述】：

我在这样的列中有一组随机文本：

dplyr::tibble(text = c("I have a (brown) clock", "surrounded by (red) walls", "inside of a (blue) building with (dirty) windows",
                      "where (magical) things (unexpectedly) occur (spontaneously)"))

# A tibble: 4 x 1
  text                                                       
  <chr>                                                      
1 I have a (brown) clock                                     
2 surrounded by (red) walls                                  
3 inside of a (blue) building with (dirty) windows           
4 where (magical) things (unexpectedly) occur (spontaneously)

我想将括号中最后出现的字符串提取到另一列中，使其看起来像这样：

dplyr::tibble(text = c("I have a (brown) clock", "surrounded by (red) walls", "inside of a (blue) building with (dirty) windows",
                          "where (magical) things (unexpectedly) occur (spontaneously)"),
                  extract = c("brown", "red", "dirty", "spontaneously"))

# A tibble: 4 x 2
  text                                                        extract      
  <chr>                                                       <chr>        
1 I have a (brown) clock                                      brown        
2 surrounded by (red) walls                                   red          
3 inside of a (blue) building with (dirty) windows            dirty        
4 where (magical) things (unexpectedly) occur (spontaneously) spontaneously

【问题讨论】：

标签： r regex dplyr stringr

【解决方案1】：

一个选项是stri_extract_last 来自stringi，它应该很快。在这里，我们进行正则表达式环顾以匹配左括号 ((?<=\\()) 后跟一个或多个不是右括号 ([^\\)]+) 的字符

library(dplyr)
df1 %>%
    mutate(extract = stringi::stri_extract_last(text, regex = "(?<=\\()[^\\)]+"))
# A tibble: 4 x 2
#  text                                                        extract      
#  <chr>                                                       <chr>        
#1 I have a (brown) clock                                      brown        
#2 surrounded by (red) walls                                   red          
#3 inside of a (blue) building with (dirty) windows            dirty        
#4 where (magical) things (unexpectedly) occur (spontaneously) spontaneously

【讨论】：