fuzzy LEFT join with R

Question

library(tidyverse)
library(fuzzyjoin)

df1 <- tibble(col1 = c("apple", "banana", "carrot"),
              col2 = as.numeric(0:2),
              col3 = as.numeric(0:2))
#> # A tibble: 3 x 3
#>   col1   col2  col3
#>   <chr> <int> <int>
#> 1 apple     0     0
#> 2 banana    1     1
#> 3 carrot    2     2

df2 <- tibble(col4 = c("app", "carr"), col5 = c(5, 9), matched = rep(TRUE, 2))
#> # A tibble: 2 x 3
#>   col4   col5 matched
#>   <chr> <dbl> <lgl>  
#> 1 app       5 TRUE   
#> 2 carr      9 TRUE 

I've got two data frames above df1 and df2. I need to create a new column for df1 that tells whether each row matches with an entry in df2, or not.

I also have to fuzzy match, and the fuzziness need to be case insensitive (hence the custom ci_str_detect function):

ci_str_detect <- function(x, y){str_detect(x, regex(y, ignore_case = TRUE))}

df1 %>% 
  fuzzy_inner_join(df2, by = c("col1" = "col4"), match_fun = ci_str_detect)
#># A tibble: 2 x 6
#>  col1    col2  col3 col4   col5 matched
#>  <chr>  <dbl> <dbl> <chr> <dbl> <lgl>  
#>1 apple      0     0 app       5 TRUE   
#>2 carrot     2     2 carr      9 TRUE 

Unfortunately (in this case) the fuzzyjoin R package appears to only do INNER JOINs, and not the LEFT JOIN that I need.

Ultimately I need this output:

#> # A tibble: 3 x 6
#>   col1    col2  col3 col4   col5  matched
#>   <chr>  <dbl> <dbl> <chr> <dbl>  <lgl>  
#> 1 apple      0     0 app       5  TRUE   
#> 2 banana     1     1 NA       NA  FALSE 
#> 3 carrot     2     2 carr      9  TRUE 

... and a LEFT JOIN would provide the intermediate data frame shown below, that I could replace NA with FALSE to get what I ultimately want (directly above).

#> # A tibble: 3 x 6
#>   col1    col2  col3 col4   col5  matched
#>   <chr>  <dbl> <dbl> <chr> <dbl>  <lgl>  
#> 1 apple      0     0 app       5  TRUE   
#> 2 banana     1     1 NA       NA  NA 
#> 3 carrot     2     2 carr      9  TRUE 

How can I fuzzy LEFT join in R?

Answer 1

Voila :)

fuzzy_left_join(df1, df2, match_fun = ci_str_detect, by = c(col1 = "col4"))