CODEWITHSUNDEEP
rregexgsub
RudiSophieson
RudiSophieson

Reputation: 271

Replace every single character at the start of string that matches a regex pattern

I want to replace every single character in a string that matches a certain pattern. Take the following string

mystring <- c("000450")

I want to match all single zeros up to the first element that is non-zero. I tried something like

gsub("^0[^1-9]*", "x", mystring)
[1] "x450"

This expression replaces all the leading zeros with a single x. But instead, I want to replace all three leading zeros with xxx. The preferred result would be

[1] "xxx450"

Can anyone help me out?

Upvotes: 9

Views: 385

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626690

You may use

mystring <- c("000450")
gsub("\\G0", "x", mystring, perl=TRUE)
## => [1] "xxx450"

See the regex demo and an R demo

The \\G0 regex matches 0 at the start of the string, and any 0 that only appears after a successful match.

Details

  • \G - an anchor that matches ("asserts") the position at the start of the string or right after a successful match
  • 0 - a 0 char.

Upvotes: 11

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