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问题描述
在 R 中，我有一个如下所示的字符串
In R I have a character string that looks like the following
x <- c("20130603 00:00:03.102","20130703 00:01:03.103","20130804 00:03:03.104")
我想通过使用单个 gsub 命令(而不是使用 substr 和 paste，但我的有限regex 知识让我无法确定我需要做什么:
I would like to to look like the following by using a single gsub command (rather than using substr and paste, but my limited regex knowledge is frustrating me in working out what i need to do to do so:
y <- gsub([REGEX PATTERN TO MATCH],[REPLACEMENT PATTERN TO INSERT HYPHEN] ,x)
> y
[1] "2013-06-03 00:00:03.102" "2013-07-03 00:01:03.103" "2013-08-04 00:03:03.104"
在我的实际示例中，x 的长度为几百万，因此任何用于提高速度的微基准测试都会有所帮助.
In my actual example, x has a length of several million, so any microbenchmarking for speed improvements would be helpful.
一如既往，不胜感激.
推荐答案
以下应该有效:
gsub("(\\d{4})(\\d{2})(\\d{2})", "\\1-\\2-\\3", subject, perl=TRUE);
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