进行模糊连接并仅在有一个时保留完全匹配，否则保留所有选项答案

【问题标题】：make a fuzzyjoin and keep only exact match when there is one, keep all options otherwise进行模糊连接并仅在有一个时保留完全匹配，否则保留所有选项
【发布时间】：2020-11-26 14:34:52
【问题描述】：

我有两个数据框，我正在尝试根据国家/地区名称字段加入，我想要实现的是：当找到完美匹配时，我想只保留那一行，否则我想显示所有行/选项。

library(fuzzyjoin)

df1 <- data.frame(
  country = c('Germany','Germany and Spain','Italy','Norway and Sweden','Austria','Spain'),
  score = c(7,8,9,10,11,12)
)

df2 <- data.frame(
  country_name = c('Germany and Spain','Germany','Germany.','Germania','Deutschland','Germany - ','Spun','Spain and Portugal','Italy','Italia','Greece and Italy',
                   'Australia','Austria...','Norway (Scandinavia)','Norway','Sweden'),
  comments = c('xxx','rrr','ttt','hhhh','gggg','jjjj','uuuuu','ooooo','yyyyyyyyyy','bbbbb','llllll','wwwwwww','nnnnnnn','cc','mmmm','lllll')
)

j <- regex_left_join(df1,df2, by = c('country' = 'country_name'), ignore_case = T)

结果 (j) 显示 'Germany and Spain' 出现了 3 次，第 1 次出现是完美匹配，我想只保留这一个并摆脱其他两个。 “挪威和瑞典”没有完美的匹配，所以我想保留两个可能的选项/行（原样）。

我该怎么做？

【问题讨论】：

标签： r join match fuzzyjoin

【解决方案1】：

您可以使用stringdist::stringdist 计算匹配项之间的距离，对于存在完全匹配项的条目，请仅保留：

library(dplyr)
j %>% 
  mutate(dist = stringdist::stringdist(country, country_name)) %>% # add distance
  group_by(country) %>%                                            # group entries
  mutate(exact = any(dist == 0)) %>%                               # check if exact match exists in group
  filter(!exact | dist == 0) %>%                                   # keep only entries where no exact match exists in the group OR where the entry is the exact match
  ungroup()
#> # A tibble: 5 x 6
#>   country           score country_name      comments    dist exact
#>   <chr>             <dbl> <chr>             <chr>      <dbl> <lgl>
#> 1 Germany               7 Germany           rrr            0 TRUE 
#> 2 Germany and Spain     8 Germany and Spain xxx            0 TRUE 
#> 3 Italy                 9 Italy             yyyyyyyyyy     0 TRUE 
#> 4 Norway and Sweden    10 Norway            mmmm          11 FALSE
#> 5 Norway and Sweden    10 Sweden            lllll         11 FALSE

【讨论】：