r - 如何使用 stringr 将两个正则表达式与 if else 结合起来

Question

问题: 大家好，我有这个示例数据框，其中包含我需要提取的机构名称:

mydf<- data.frame(ID=c('1', '2', '3'), Institution=c('Univ of Space, TX, US', '[Bloggs, J., Smith, T.] Univ of Time, CA, US', '[Windz, P., Lol, D.] College of the World, CA, US' ))

我只需要提取机构名称，使其显示如下:

1 Univ of Space
2 Univ of Time
3 College of the World

我不关心机构字符串中的任何其他字符，只关心第一个逗号之前的所有字符。问题是我在某些情况下机构名称前面会加一个括号，有时会单独出现(如第一行的情况)。

我编写了以下代码来分别提取这两个实例:

ex_inst<- str_extract_all(mydf$Institution,"(?<=])(.+?)(?=,)", simplify = TRUE)
ex_inst2<- str_extract_all(mydf$Institution,"^(.+?)(?=,)", simplify = TRUE)

我正在努力将它们结合在一起。我研究了交替，并尝试了这个

ex_inst3<- str_extract_all(mydf$Institution,"^(.+?)(?=,)|(?<=])(.+?)(?=,)", simplify = TRUE)

但我对正则表达式没有经验，并且对它的输出内容感到困惑:

[1,] "Univ of Space" ""                     
[2,] "[Bloggs"       " Univ of Time"        
[3,] "[Windz"        " College of the World"

将其与 stringr 结合的最佳方法是什么，我可以使用某种 if else 语句吗？ 谢谢。

Answer 1

我们可以使用str_replace来捕获不是,的字符，同时删除方括号内(包括方括号)内的任何字符

library(stringr)
str_replace(mydf$Institution,"^(\\[[^]]*\\]\\s*)?([^,]+),.*", "\\2")
#[1] "Univ of Space"        "Univ of Time"         "College of the World"

---

或者使用与 sub 相同的模式

sub("^(\\[[^]]*\\]\\s*)?([^,]+),.*", "\\2", mydf$Institution)
#[1] "Univ of Space"        "Univ of Time"         "College of the World"

更新

如果我们有多个条目，可以选择将其拆分为多个组件，然后使用与上面相同的代码

v1 <- unlist(strsplit(as.character(mydf$Institution), ";\\s(?=\\[)", perl = TRUE))
sub("^(\\[[^]]*\\]\\s*)?([^,]+),.*", "\\2", v1)
#[1] "Univ of Space"        "Univ of Time"         
#[3] "College of the World" "College of the World" "Space Institute"  

---

如果我们需要附加为新列

lst1 <- setNames(strsplit(as.character(mydf$Institution), 
      ";\\s(?=\\[)", perl = TRUE), mydf$ID)
mydf2 <- stack(lst1)
mydf2$values <- sub("^(\\[[^]]*\\]\\s*)?([^,]+),.*", "\\2", stack(lst1)$values)
out1 <- aggregate(values ~ ., merge(mydf, mydf2, by.x = "ID", by.y = "ind"),
      FUN = paste, collapse = '; ')
out1[order(as.numeric(out1$ID)),]
#  ID                                                                                      Institution                                values
#4  1                                                                            Univ of Space, TX, US                         Univ of Space
#1  2                                                     [Bloggs, J., Smith, T.] Univ of Time, CA, US                          Univ of Time
#2  3                                                [Windz, P., Lol, D.] College of the World, CA, US                  College of the World
#3  4 [Windz, P., Lol, D.] College of the World, CA, US; [Bon, D.; Wilson, M.] Space Institute, TX, US College of the World; Space Institute

数据

mydf <- structure(list(ID = c("1", "2", "3", "4"), Institution = c("Univ of Space, TX, US", 
"[Bloggs, J., Smith, T.] Univ of Time, CA, US", "[Windz, P., Lol, D.] College of the World, CA, US", 
"[Windz, P., Lol, D.] College of the World, CA, US; [Bon, D.; Wilson, M.] Space Institute, TX, US"
)), class = "data.frame", row.names = c(NA, -4L))

注意:更新了评论中的数据