使用gsub删除多个空格和尾部空格 [英] Removing multiple spaces and trailing spaces using gsub

问题描述

如何仅用1个gsub删除多个空格和尾随空格?我已经将此函数设置为trim <- function(x) gsub(' {2,}',' ',gsub('^ *| *$','',x))，但是我正试图仅用1个gsub重写它.

How can I remove multiple spaces and trailing spaces using only 1 gsub? I already made this function trim <- function(x) gsub(' {2,}',' ',gsub('^ *| *$','',x)), but i'm trying to rewrite it with only 1 gsub.

实际上，我想根据gsub的前后关系来确定如何进行匹配.在此示例中，我需要匹配以单个空格开头的所有空格，并用''

Actually, I want lean how to match something based in what is after/before it with gsub. In this example I need to match all spaces that are preceeded by a single space, and replace them by ''

推荐答案

使用正向后方查找当前空间是否以空格开头:

Use a positive lookbehind to see if the current space is preceded by a space:

^ *|(?<= ) | *$

在此处查看操作: http://regex101.com/r/bJ1mU0

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