回顾后在str_extract有R

我回顾后在str_extract有R

[01/29/14 16:42:55, 10.100.120.120, unknown]: spatial_monitor: Alan entered Conference Room (Zone Role contains Person role) 
[01/29/14 16:42:57, 10.100.120.120, unknown]: spatial_monitor: Alan left Conference Room (Zone Role contains Person role) 
[01/29/14 16:43:00, 10.100.120.120, unknown]: spatial_monitor: Kurt entered Conference Room (Computer desk contains Person role) 
[01/29/14 16:43:02, 10.100.120.120, unknown]: spatial_monitor: Kurt left Conference Room (Computer desk contains Person role) 
[01/29/14 16:43:03, 10.100.120.120, unknown]: spatial_monitor: Alan entered Conference Room (Zone Role contains Person role) 
[01/29/14 16:43:08, 10.100.120.120, unknown]: spatial_monitor: Alan left Conference Room (Zone Role contains Person role) 
[01/29/14 16:46:07, 10.100.120.120, unknown]: spatial_monitor: Fred entered Conference Room (Zone Role contains Person role) 
[01/29/14 16:46:08, 10.100.120.120, unknown]: spatial_monitor: Fred left Conference Room (Zone Role contains Person role)

我想使用R中str_extract（库stringr）提取的位置（“会议室”上面的例子中）的名称下面的文本文件。逻辑是拉动字词“进入”或“离开”后面的部分。为此，我有以下的正则表达式

(?<=entered\s)[A-Z][a-z]+\s[A-Z][a-z]+

这在记事本++工作正常，但是当我嵌入此R中，我得到以下错误

> tt <- "[01/29/14 16:42:55, 10.100.120.120, unknown]: spatial_monitor: Alan entered Conference Room (Zone Role contains Person role)" 
> str_extract(tt, '(?<=entered\\s)[A-Z][a-z]+\\s[A-Z][a-z]+') 
Error in regexpr("(?<=entered\\s)[A-Z][a-z]+\\s[A-Z][a-z]+", "[01/29/14 16:42:55, 10.100.120.120, unknown]: spatial_monitor: Alan entered Conference Room (Zone Role contains Person role)", : 
    invalid regular expression '(?<=entered\s)[A-Z][a-z]+\s[A-Z][a-z]+', reason 'Invalid regexp'

其他答案告诉我，lookahead and lookbehind only work with Perl。所以问题是如何使用str_extract来启用Perl？或者有更好的方法来做到这一点？提前致谢。

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2014-02-06 Bala Deshpande

这个工作并没有采用前瞻/回顾后。如图所示，将要提取的部分括起来：'library（gsubfn）; strapplyc（tt，'entered \\ s（[A-Z] [a-z] + \\ s [A-Z] [a-z] +）'，simplify = TRUE）' –

library(stringr) 
tt <- "[01/29/14 16:42:55, 10.100.120.120, unknown]: spatial_monitor: Alan entered Conference Room (Zone Role contains Person role)" 
str_extract(tt, perl('(?<=entered\\s)[A-Z][a-z]+\\s[A-Z][a-z]+')) 
# [1] "Conference Room"

来源

2014-02-06 15:39:20 lukeA

太棒了！感谢帮助。谢谢。 –

@BalaDeshpande我的荣幸。 Simafore博客曾帮助我发现RapidMiner。 :) – lukeA

你的正则表达式是有效。如果您指定perl = TRUE，它适用于sub。您也可以使用sub功能，为您的任务：

sub('.*(?<=entered\\s)([A-Z][a-z]+\\s[A-Z][a-z]+).*', '\\1', tt, perl = TRUE) 
# [1] "Conference Room"

另外，不perl：

sub('.*entered\\s([A-Z][a-z]+\\s[A-Z][a-z]+).*', '\\1', tt) 
# [1] "Conference Room"

来源

2014-02-06 15:37:54

感谢您提供替代方案。我有upvoted。不过，我喜欢其他答案。 –

回顾后在str_extract有R

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