regex - strsplit by parentheses -

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• regular expression string between parentheses in javascript 5 answers

suppose have string "a b c (123-456-789)", i'm wondering what's best way retrieve "123-456-789" it.

strsplit("a b c (123-456-789)", "\\(") [[1]] [1] "a b c" "123-456-789)" 

if want extract digits - between braces, 1 option str_extract. if there multiple patterns within string, use str_extract_all

 library(stringr)  str_extract(str1, '(?<=\\()[0-9-]+(?=\\))')  #[1] "123-456-789"  str_extract_all(str2, '(?<=\\()[0-9-]+(?=\\))') 

in above codes, using regex lookarounds extract numbers , -. positive lookbehind (?<=\\()[0-9-]+ matches numbers along - ([0-9-]+) in (123-456-789 , not in 123-456-789. lookahead ('[0-9-]+(?=\)') matches numbers along - in 123-456-789) , not in 123-456-798. taken matches cases satisfy both conditions (123-456-789) , extract in between lookarounds , not cases (123-456-789 or 123-456-789)

with strsplit can specify split [()]. keep () inside square brackets [] treat characters or else have escape parentheses ('\\(|\\)').

 strsplit(str1, '[()]')[[1]][2]  #[1] "123-456-789" 

if there multiple substrings extract string, loop lapply , extract numeric split parts grep

 lapply(strsplit(str2, '[()]'), function(x) grep('\\d', x, value=true)) 

or can use stri_split stringi has option remove empty strings (omit_empty=true).

 library(stringi)  stri_split_regex(str1, '[()a-z ]', omit_empty=true)[[1]]  #[1] "123-456-789"   stri_split_regex(str2, '[()a-z ]', omit_empty=true) 

another option rm_round qdapregex if interested in extracting contents inside brackets.

 library(qdapregex)  rm_round(str1, extract=true)[[1]]  #[1] "123-456-789"  rm_round(str2, extract=true) 

data

 str1 <-  "a b c (123-456-789)"  str2 <- c("a b c (123-425-478) a", "abc(123-423-428)",  "(123-423-498) abcdd",    "(123-432-423)", "abc (123-423-389) gr (124-233-848) ak")