R:gsub/仅替换关键字出现后的那些出现 [英] R: gsub/replace only those occurrences following a keyword occurrence

问题描述

我只想替换出现在特定关键字/模式之后而不是之前的字符串.换句话说，在第一次出现关键字模式之前，什么也不做，然后在该关键字模式的右边开始gsub.见下文:

I only want to replace string occurrences that follow a particular keyword/pattern and not before. in other words, do nothing until the first occurrence of the keyword-pattern, and then start to gsub to the right of that keyword-pattern. See below:

gsub("\\[|\\]", "", "ab[ cd] ef keyword [ gh ]keyword ij ")

实际结果: "ab cd ef关键字gh关键字ij"

Actual results: "ab cd ef keyword gh keyword ij "

所需结果: "ab [cd] [] [asfg]]] ef关键字gh关键字ij"

Desired results: "ab[ cd] [][asfg] ]] ef keyword gh keyword ij "

[已编辑以修复结果.我不想删除关键字"]

推荐答案

您可以使用\G在关键字后获取连续的匹配项.使用\K忘记匹配的内容，并匹配以下[或]以替换为空字符串.

You might use \G to get continous matches after keyword. Use \K to forget what was matched and match the following [ or ] to be replaced with an empty string.

(?:^.*?keyword\b|\G(?!^))[^\[\]]*\K[\[\]]

部分

• (?:非捕获组
  • ^.*?keyword匹配直到第一个关键字
  • |或
  • \G(?!^)在上一场比赛的末尾断言位置，而不是在开始连续比赛的末尾断言
  • (?: Non capturing group
    • ^.*?keyword Match until the first keyword
    • | Or
    • \G(?!^) Assert position at the end of previous match, not at the start to get continuous matches

    正则表达式演示 | R演示

    您的代码可能看起来像

    gsub("(?:^.*?keyword\\b|\\G(?!^))[^\\[\\]]*\\K[\\[\\]]", "", "ab[ cd] ef keyword [ gh ]keyword ij ", perl=T)
    

    请注意，对于类似Perl的正则表达式，请最后使用perl=T.

    Note to use perl=T at the end for Perl-like regular expressions.

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