R - replace part of a string using wildcards

Question

I just started using R again, and I was wondering is there a way to replace part of a string using wildcards.

For example:

say I have

S1 <- "aaaaaaaaa[aaaaa]aaaa[bbbbbbb]aaaa" 

and I want to replace everything within square brackets with 'x', such that the new string is

"aaaaaaaaa[x]aaaa[x]aaaa" 

Is this possible to do in R?

Please note what is in the square bracket can be of variable length.

Answer 1

A simple regex would be like

\\[.+?\\]

Example http://regex101.com/r/xE1rL1/1

Example Usage

s1 <- 'aaaaaaaaa[aaaaa]aaaa[bbbbbbb]aaaa'
gsub("\\[.+?\\]", "[x]", s1)
## [1] "aaaaaaaaa[x]aaaa[x]aaaa"

Regular expression

• \\[ matches opening [

• .+? non greedy matching of anything

• \\] matches closing ]

EDIT

For safety, if nothing is present in the the [], then the regex can be slightly modified as

s1 <- 'aaaaaaaaa[]aaaa[bbbbbbb]aaaa'
gsub("\\[.*?\\]", "[x]", s1)
##[1] "aaaaaaaaa[x]aaaa[x]aaaa"

Answer 2

Could also try qdapRegex package which has a special method for such problems: rm_square

library(qdapRegex)
S1 <- "aaaaaaaaa[aaaaa]aaaa[bbbbbbb]aaaa" 
rm_square(S1, replacement = "[x]")
## [1] "aaaaaaaaa[x]aaaa[x]aaaa"

Will work the same for empty brackets

S1 <- "aaaaaaaaa[]aaaa[bbbbbbb]aaaa" 
rm_square(S1, replacement = "[x]")
## [1] "aaaaaaaaa[x]aaaa[x]aaaa"