Need to remove some specific string from a column using R script [closed]

A few things wrong.

1) Don't use brackets here. In regex, [abc] matches a or b or c. You want to match the whole pattern, so don't use brackets. (You could use parenthesis, but it it not necessary

"\\ (more info)"  # fix 1: no brackets

2) You seem to know backslashes are used to escape things in regex. But they must be next to what they are escaping! Here you are escaping a space, which is meaningless. You need to escape both parentheses that are part of your pattern:

"\\(more info\\)"  # fix 2: escape parens

3) You still need the space, but it goes at the front, before the (escaped) parenthesis:

" \\(more info\\)"  # fix 3: space at beginning 

Now the pattern should work. Also note that gsub returns a character, so your as.character is redundant.

I'd strongly recommend using a site like regex101.com to debug regex. You only need single \ to escape there, but other than that it is just like R. Here's your example. Check out the sidebar for nice explanations.