regex - R正则表达式删除除字母、撇号和指定的多字符字符串之外的所有内容

Question

是否有 R 正则表达式可以删除除字母、撇号和指定的多字符字符串以外的所有内容？ “指定的多字符串”是任意的，任意长度。比方说 "~~" & && 在这种情况下(所以 ~ & & 应该被删除但不是 ~~ & &&)

我这里有:

gsub("[^ a-zA-Z']", "", "I like~~cake~too&&much&now.")

给出:

## [1] "I like~~cake~toomuchnow"

还有……

gsub("[^ a-zA-Z'~&]", "", "I like~~cake~too&&much&now.")

给...

## "I like~~cake~too&&much&now"

我如何编写一个 R 正则表达式来给出:

"I like~~caketoo&&muchnow"

编辑 Casimir 和 BrodieG 的极端案例...

我期望这种行为:

x <- c("I like~~cake~too&&much&now.", "a~~~b", "a~~~~b", "a~~~~~b", "a~&a")

## [1] "I like~~caketoo&&muchnow." "a~~b"                     
## [3] "a~~~~b"                    "a~~~~b"                   
## [5] "aa" 

当前的方法都没有给出这一点。

Answer 1

一种方法，匹配/捕获“指定的多字符字符串”，同时替换其他字符串。

gsub("(~~|&&)|[^a-zA-Z' ]", "\\1", x)

# [1] "I like~~caketoo&&muchnow" "a~~b"                    
# [3] "a~~~~b"                   "a~~~~b"                  
# [5] "aa"