替换与正则表达式模式匹配的字符串开头的每个单个字符 [英] Replace every single character at the start of string that matches a regex pattern

问题描述

我想替换匹配特定模式的字符串中的每个单个字符.取以下字符串

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

mystring <- c("000450")

我想将所有单个零匹配到第一个非零元素.我尝试过类似的

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"

此表达式用单个x替换所有前导零.但是，我想用xxx替换所有三个前导零.首选结果将是

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"

有人可以帮我吗?

推荐答案

您可以使用

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

请参见 regex演示和 \\G0正则表达式在字符串的开头与0匹配，并且仅在成功匹配之后出现的任何0.

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

详细信息

• \G-匹配(断言")字符串开头或匹配成功后位置的锚点
• 0-一个0字符.

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

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