我有一些高度非结构化的日期数据，其中包含许多错误。目前，我的regex捕获语法在获取所有日期方面非常出色，但它也可以捕获不是日期的数字。这些数字后面通常带有表示法，这些符号应有助于预测这些数字是某种数字还是日期。
uglydates = c(
"05-01-2018 Worked on PP&E valve. Specimens are unusually active.",
"55.2 psi containment pressure nominal.",
"August 11, 2018 Personal Journal, I thought I would like being alone. I was wrong.",
"34.1 PSI reported on containment unit 34. Loss of pressure, cause unknown.",
"10 3/4 casing seems to have ruptured. Exterior has numerous punctures",
"perhaps caused by a wild animal.",
"1.06.19 Hearing chittering noises in the woods.",
"Thursday, February 2, 2019 Returned to Bunker, Mr. Higglies is missing.",
"Fri, February 3, 2019 through Sunday, February 5, 2019 Searched for Mr. Higglies",
"Thursday, Feb 9, 19 What remained of Mr. Higglies found me...",
"Bleeding profusely, returning to the silo.",
"Friday, 2 27 19 - Have not been able to stop bleeding. Don't feel like eating.",
"Leaving bunker in search of help.",
"3 27 Can't walk any longer. Going to lie here for just a few minutes.")
library(dplyr)
library(stringr)
# Function for adding parentheses around text
par <- function(x) paste0("(",x,")")
months <- month.name %>% paste(collapse= "|") %>% par
monab <- month.abb %>% paste(collapse= "|") %>% par
days <- (Sys.Date() + (0:6)) %>% format("%A") %>% paste(collapse= "|") %>% par
dayab <- (Sys.Date() + (0:6)) %>% format("%a") %>% paste(collapse= "|") %>% par
num <- "([1-9]|[0-3][0-9]|201[6-9])" # 01-39, 1-9, 2016-2018
daydate <- paste(days, dayab, months, monab, num, sep= "|") %>% par
sep <-"[/\\-\\s/\\.,]*" # seperators
end <- "[\\s:\\-\\.\n$]" # Define possible end values
datematch <- paste0("^(?i)(",daydate,sep,"){1,5}(",end,")")
#"^(?i)(((Wednesday|Thursday|Friday|Saturday|Sunday|Monday|Tuesday)|(Wed|Thu|Fri|Sat|Sun|Mon|Tue)|(January|February|March|April|May|June|July|August|September|October|November|December)|(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)|([1-9]|[0-3][0-9]|201[6-9]))[/\\-\\s/\\.,]*){1,5}([\\s:\\-\\.\n$])"
uglydates %>% str_extract(datematch)
# [1] "05-01-2018 " "55.2 " "August 11, 2018 "
# [4] "34.1 " "10 3/4 " NA
# [7] "1.06.19 " "Thursday, February 2, 2019 " "Fri, February 3, 2019 "
# [10] "Thursday, Feb 9, 19 " NA "Friday, 2 27 19 - "
# [13] NA "3 27 "
我尝试使用否定的前瞻性?!...语法，但是它似乎并不能抵消我需要的所有内容（捕获整个字符串）。
exclude = "(PSI|casing)"
datematch <- paste0("^(?i)((",daydate,sep,"){1,5}(",end,"))(?!", exclude,")")
# "^(?i)((((Wednesday|Thursday|Friday|Saturday|Sunday|Monday|Tuesday)|(Wed|Thu|Fri|Sat|Sun|Mon|Tue)|(January|February|March|April|May|June|July|August|September|October|November|December)|(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)|([1-9]|[0-3][0-9]|201[6-9]))[/\\-\\s/\\.,]*){1,5}([\\s:\\-\\.\n$]))(?!(PSI|casing))"
uglydates %>% str_extract(datematch)
# [1] "05-01-2018 " "55." "August 11, 2018 "
# [4] "34." "10 " NA
# [7] "1.06.19 " "Thursday, February 2, 2019 " "Fri, February 3, 2019 "
# [10] "Thursday, Feb 9, 19 " NA "Friday, 2 27 19 - "
# [13] NA "3 27 "
答案 0 :(得分：1)
如本虚拟示例所示，当前的否定前行仅否定最终匹配的可选组，另请参见例如Regular expression with optional part and negative lookahead
str_extract("0-0-0 psi", "((0[-]?)+)(?!\\spsi)")
#> [1] "0-0-"
由reprex package（v0.3.0）于2019-06-13创建
一个简单的解决方案是替换：
exclude <- "(.*(PSI|casing))"
如果找到PSI或casing，则将否定整个字符串捕获：
uglydates = c(
"05-01-2018 Worked on PP&E valve. Specimens are unusually active.",
"55.2 psi containment pressure nominal.",
"August 11, 2018 Personal Journal, I thought I would like being alone. I was wrong.",
"34.1 PSI reported on containment unit 34. Loss of pressure, cause unknown.",
"10 3/4 casing seems to have ruptured. Exterior has numerous punctures",
"perhaps caused by a wild animal.",
"1.06.19 Hearing chittering noises in the woods.",
"Thursday, February 2, 2019 Returned to Bunker, Mr. Higglies is missing.",
"Fri, February 3, 2019 through Sunday, February 5, 2019 Searched for Mr. Higglies",
"Thursday, Feb 9, 19 What remained of Mr. Higglies found me...",
"Bleeding profusely, returning to the silo.",
"Friday, 2 27 19 - Have not been able to stop bleeding. Don't feel like eating.",
"Leaving bunker in search of help.",
"3 27 Can't walk any longer. Going to lie here for just a few minutes.")
library(dplyr)
library(stringr)
# Function for adding parentheses around text
par <- function(x) paste0("(",x,")")
months <- month.name %>% paste(collapse= "|") %>% par
monab <- month.abb %>% paste(collapse= "|") %>% par
days <- (Sys.Date() + (0:6)) %>% format("%A") %>% paste(collapse= "|") %>% par
dayab <- (Sys.Date() + (0:6)) %>% format("%a") %>% paste(collapse= "|") %>% par
num <- "([1-9]|[0-3][0-9]|201[6-9])" # 01-39, 1-9, 2016-2018
daydate <- paste(days, dayab, months, monab, num, sep= "|") %>% par
sep <-"[/\\-\\s/\\.,]*" # seperators
end <- "[\\s:\\-\\.\n$]" # Define possible end values
exclude <- "(.*(PSI|casing))"
datematch <- paste0("^(?i)((",daydate,sep,"){1,5}(",end,"))(?!", exclude,")")
# "^(?i)((((Wednesday|Thursday|Friday|Saturday|Sunday|Monday|Tuesday)|(Wed|Thu|Fri|Sat|Sun|Mon|Tue)|(January|February|March|April|May|June|July|August|September|October|November|December)|(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)|([1-9]|[0-3][0-9]|201[6-9]))[/\\-\\s/\\.,]*){1,5}([\\s:\\-\\.\n$]))(?!(.*(PSI|casing)))"
uglydates %>% str_extract(datematch)
#> [1] "05-01-2018 " NA
#> [3] "August 11, 2018 " NA
#> [5] NA NA
#> [7] "1.06.19 " "Thursday, February 2, 2019 "
#> [9] "Fri, February 3, 2019 " "Thursday, Feb 9, 19 "
#> [11] NA "Friday, 2 27 19 - "
#> [13] NA "3 27 "
由reprex package（v0.3.0）于2019-06-13创建