回顧後在str_extract有R

我回顧後在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（庫stringr）提取的位置（「會議室」上面的例子中）的名稱下面的文本文件。邏輯是拉動字詞「進入」或「離開」後面的部分。爲此，我有以下的正則表達式

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

這在記事本++工作正常，但是當我嵌入此R中，我得到以下錯誤

> 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'

其他答案告訴我，lookahead and lookbehind only work with Perl。所以問題是如何使用str_extract來啓用Perl？或者有更好的方法來做到這一點？提前致謝。

來源

2014-02-06 Bala Deshpande

這個工作並沒有採用前瞻/回顧後。如圖所示，將要提取的部分括起來：'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"

來源

2014-02-06 15:39:20 lukeA

太棒了！感謝幫助。謝謝。 –

@BalaDeshpande我的榮幸。 Simafore博客曾幫助我發現RapidMiner。 :) – lukeA

你的正則表達式是有效。如果您指定perl = TRUE，它適用於sub。您也可以使用sub功能，爲您的任務：

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"

來源

2014-02-06 15:37:54

感謝您提供替代方案。我有upvoted。不過，我喜歡其他答案。 –

回顧後在str_extract有R

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