英文:
separate_wider_regex with lookahead
问题
我有一个包含体育赛事的数据框架（对于空格或单词数量没有假设），其中可以选择包含年份，并且可能以几种不同的方式格式化。
tibble::tibble(event_optional_year = c("World Championships", "Summer Olympics 12", "Olympics 2016", "Olympics 2020/221"))
我如何使用 tidyr::separate_wider_regex 来将 event_optional_year 拆分为两列 event 和 year？在这种情况下，我希望 event 被剥离出可选的年份，而 year 分别等于 NA、12、2016 和 2020/2021。
我尝试了在正则表达式中使用正向先行：
tibble::tibble(event_optional_year = c("Olympics", "Olympics 12", "Olympics 2016", "Olympics 2020/221")) |>tidyr::separate_wider_regex("event_optional_year",c(event = ".*(?=(?:\\d.*\\d$)?)",year = "\\d.*\\d$"),too_few = "align_start")
但这给出了如下结果：
event year<chr> <chr>1 "World Championships" NA2 "Summer Olympics " 123 "Olympics 20" 164 "Olympics 2020/2" 21
问题：哪个正则表达式可以给我所需的结果？
英文:
I have a dataframe with sporting events (with no assumptions about the number of spaces or words) with an optional year, that can be formatted in a few different ways.
tibble::tibble(event_optional_year = c("World Championships", "Summer Olympics 12", "Olympics 2016", "Olympics 2020/221"))
How can I use tidyr::separate_wider_regex to split event_optional_year into two columns event and year? I want event in this case to be stripped of the optional year, and year equal to NA, 12, 2016 and 2020/2021, respectively.
I tried fiddling with positive lookahead in the regex:
tibble::tibble(event_optional_year = c("Olympics", "Olympics 12", "Olympics 2016", "Olympics 2020/221")) |>tidyr::separate_wider_regex("event_optional_year",c(event = ".*(?=(?:\\d.*\\d$)?)",year = "\\d.*\\d$"),too_few = "align_start")
but this gives as result:
event year<chr> <chr>1 "World Championships" NA2 "Summer Olympics " 123 "Olympics 20" 164 "Olympics 2020/2" 21
Question: which regex does give me the desired result?
答案1
得分: 3
separate_wider_regex()中的未命名模式简化了这个情况。event = ".*"是贪婪的，匹配了"\\s+(?=\\d)"之前的所有内容——任意数量的空格，紧跟着一个数字（假设year部分以数字开头）。这处理了event中的空格，但假设year中没有空格。
library(dplyr)library(tidyr)tibble(event_optional_year = c("World Championships","Summer Olympics 12","Olympics 2016","Olympics 2020/221")) %>%separate_wider_regex(event_optional_year,c(event = ".*", "\\s+(?=\\d)", year = ".*$") ,too_few = "align_start")#> # A tibble: 4 × 2#> event year#> <chr> <chr>#> 1 World Championships <NA>#> 2 Summer Olympics 12#> 3 Olympics 2016#> 4 Olympics 2020/221
<sup>创建于2023年6月25日，使用reprex v2.0.2</sup>
英文:
Unnamed patterns in separate_wider_regex() simplify this situation a bit. event = ".*" is greedy and matches everything before "\\s+(?=\\d)" -- any number of whitespace that is followed by a digit (assuming that year-part starts with a digit). This handles spaces in event but assumes there are none in year.
library(dplyr)library(tidyr)tibble(event_optional_year = c("World Championships","Summer Olympics 12","Olympics 2016","Olympics 2020/221")) %>%separate_wider_regex(event_optional_year,c(event = ".*", "\\s+(?=\\d)", year = ".*$") ,too_few = "align_start")#> # A tibble: 4 × 2#> event year#> <chr> <chr>#> 1 World Championships <NA>#> 2 Summer Olympics 12#> 3 Olympics 2016#> 4 Olympics 2020/221
<sup>Created on 2023-06-25 with reprex v2.0.2</sup>
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