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  1. test.dat <- c("abcde", "abcXe", "abcdY", "abcXY")
  2. gsub("(XY?|Y)", "1\\1", test.dat)
  3.  
  4. library(stringr)
  5. str_replace_all(test.dat, "(XY?|Y)", "1\\1")
Success #stdin #stdout 0.29s 42800KB
comments (?)
stdin 
Standard input is empty
stdout 
[1] "abcde"  "abc1Xe" "abcd1Y" "abc1XY"
[1] "abcde"  "abc1Xe" "abcd1Y" "abc1XY"
https://ideone.com/r13zZ9
language:
R (R 3.5.2)
created:
4 years ago
visibility:
secret

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