提取與正則表達式的一個日期，它可能會或可能不會也含有時間

Question

請考慮以下

library(stringr) 

text <- c("blabla bla blabla bla 6:05, 15 July 2005, blabla bla", 
      "blabla bla bla 7:06, 3 November 2006, blabla bla", 
      "blabla bla 24 November 2006, blabla bla", 
      "blabla bla blabla bla bla blabla bla") 

dates <- str_extract_all(text, ???) 

我試圖從向量提取所有日期，並在情況下，他們與時間也是時間。

Answer 1

下次嘗試顯示您嘗試的內容。下面的作品，但可能有更有效的正則表達式模式可能

pat <- paste0("([0-9]{1,2}:[0-9]{2},)*[0-9]{1,2} (", paste(month.name, collapse = "|"), ") [0-9]{4}") 

pat 
## [1] "([0-9]{1,2}:[0-9]{2},)*[0-9]{1,2} (January|February|March|April|May|June|July|August|September|October|November|December) [0-9]{4}" 


regmatches(text, gregexpr(pat, text = text)) 
## [[1]] 
## [1] "6:05, 15 July 2005" 
## 
## [[2]] 
## [1] "7:06, 3 November 2006" 
## 
## [[3]] 
## [1] "24 November 2006" 
## 
## [[4]] 
## character(0) 
## 


# or using stringr package 

str_extract_all(text, pat) 
## [[1]] 
## [1] "6:05, 15 July 2005" 
## 
## [[2]] 
## [1] "7:06, 3 November 2006" 
## 
## [[3]] 
## [1] "24 November 2006" 
## 
## [[4]] 
## character(0) 
##