Remove all punctuation except underline between characters in R with POSIX character class

Question

I would like to use R to remove all underlines expect those between words. At the end the code removes underlines at the end or at the beginning of a word. The result should be 'hello_world and hello_world'. I want to use those pre-built classes. Right know I have learn to expect particular characters with following code but I don't know how to use the word boundary sequences.

test<-"hello_world and _hello_world_"
gsub("[^_[:^punct:]]", "", test, perl=T)

Answer 1

You can use

gsub("[^_[:^punct:]]|_+\\b|\\b_+", "", test, perl=TRUE)

See the regex demo

Details:

• [^_[:^punct:]] - any punctuation except _
• | - or
• _+\b - one or more _ at the end of a word
• | - or
• \b_+ - one or more _ at the start of a word