regex - R正则表达式提取文本不紧跟模式

Question

我有一个数据框，其中有一列包含半结构化文本。我正在寻找某些信息，但它们具有我不确定如何利用的模式。

head(events5)
     flight_history_id         date_time_recorded              event
862          280604281 2012-11-13 17:55:58.673-08 Arrival Estimation
5514         280316415 2012-11-12 17:25:08.814-08    Time Adjustment
5527         280315758 2012-11-12 16:10:06.968-08    Time Adjustment
5539         280316495 2012-11-12 15:38:10.099-08    Time Adjustment
5545         280303866 2012-11-13 06:51:45.831-08    Time Adjustment
5558         280303866 2012-11-12 05:50:23.547-08    Time Adjustment
                                                                               data_updated
862                                                     EGA- Based on Distance and Airspeed
5514                        EGD- New=11/13/12 20:20, DGATE- New=A1, EGA- New=11/13/12 21:00
5527         EGD- New=11/13/12 19:05, DGATE- New=A7, EGA- New=11/13/12 20:50, AGATE- New=C5
5539                        EGD- New=11/13/12 06:35, DGATE- New=A1, EGA- New=11/13/12 07:15
5545 AGD- Old=11/13/12 07:40 New=11/13/12 07:38, EGA- Old=11/13/12 10:25 New=11/13/12 10:18
5558         EGD- New=11/13/12 07:45, DGATE- New=11, EGA- New=11/13/12 10:25, AGATE- New=A1

这是输出:

structure(list(flight_history_id = c(280604281L, 280316415L, 
280315758L, 280316495L, 280303866L, 280303866L, 280271465L, 280271465L, 
280271465L, 280271465L), date_time_recorded = structure(c(10L, 
4L, 3L, 2L, 7L, 1L, 9L, 8L, 6L, 5L), .Label = c("2012-11-12 05:50:23.547-08", 
"2012-11-12 15:38:10.099-08", "2012-11-12 16:10:06.968-08", "2012-11-12 17:25:08.814-08", 
"2012-11-12 17:58:14.268-08", "2012-11-13 05:16:41.01-08", "2012-11-13 06:51:45.831-08", 
"2012-11-13 07:38:19.593-08", "2012-11-13 07:54:22.588-08", "2012-11-13 17:55:58.673-08"
), class = "factor"), event = structure(c(1L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L), .Label = c("Arrival Estimation", "Time Adjustment"
), class = "factor"), data_updated = structure(c(3L, 8L, 7L, 
4L, 2L, 5L, 1L, 10L, 9L, 6L), .Label = c("AGD- New=11/13/12 10:22, EGA- Old=11/13/12 11:20 New=11/13/12 11:09", 
"AGD- Old=11/13/12 07:40 New=11/13/12 07:38, EGA- Old=11/13/12 10:25 New=11/13/12 10:18", 
"EGA- Based on Distance and Airspeed", "EGD- New=11/13/12 06:35, DGATE- New=A1, EGA- New=11/13/12 07:15", 
"EGD- New=11/13/12 07:45, DGATE- New=11, EGA- New=11/13/12 10:25, AGATE- New=A1", 
"EGD- New=11/13/12 08:55, EGA- New=11/13/12 09:45, AGATE- New=A1", 
"EGD- New=11/13/12 19:05, DGATE- New=A7, EGA- New=11/13/12 20:50, AGATE- New=C5", 
"EGD- New=11/13/12 20:20, DGATE- New=A1, EGA- New=11/13/12 21:00", 
"EGD- Old=11/13/12 08:55 New=11/13/12 10:05, EGA- Old=11/13/12 09:45 New=11/13/12 10:55", 
"EGD- Old=11/13/12 10:05 New=11/13/12 10:30, EGA- Old=11/13/12 10:55 New=11/13/12 11:20"
), class = "factor")), .Names = c("flight_history_id", "date_time_recorded", 
"event", "data_updated"), row.names = c(862L, 5514L, 5527L, 5539L, 
5545L, 5558L, 5564L, 5566L, 5570L, 5572L), class = "data.frame")

我正在尝试从 'data_updated' 列中提取以 'EGA' 开头的部分的字段 'New=' 部分>。问题是有时两者之间有一个“Old=”字段。我查看了使用 stringr::str_split 并将列转换为列表，但仍然有同样的问题。我认为这是一个正则表达式/gsub 问题，但不知 Prop 体如何实现。

有什么建议吗？

编辑:我希望最终产品是具有 EGA/新值的向量/列。所以像这样:

NA
11/13/12 21:00
11/13/12 20:50
11/13/12 07:15
11/13/12 10:18
11/13/12 10:25

Answer 1

与@Pharaoh 的正则表达式相比，这是一个替代方案，它在 EGA-tag

之后使用无限量的文本

/EGA-(?:(?!New=|").)+(New=[:\d\/ ]+)/g

如果否定前瞻中的 " 过于笼统，您可以将其更改为 EGD。

演示+说明: http://regex101.com/r/qY4uA0

如果不需要，请删除标志和分隔符。