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  1. string <- c("[1] cate 1", "[-1] cate -1", "[2] cate 2")
  2. stringr::str_extract(string, "(?<=\\[)-?\\d+(?=\\])")
  3. ## =>  "1"  "-1" "2" 
  4.  
Success #stdin #stdout 0.38s 41596KB
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[1] "1"  "-1" "2"
https://ideone.com/DJyBRM
language:
R (R 3.5.2)
created:
4 years ago
visibility:
secret

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