Vectorized function for dplyr::mutate()

Question

I am trying to write a vectorized function to compare a string to a vector of regular expressions and return TRUE if the string matches any of the regular expressions. The function should work on a single string, a vector of strings, and within dplyr::mutate. I'm having trouble vectorizing the function. In the below reprex, the function I would like to vectorize is is_favorite. I came up with work-arounds using base::Vectorize and purrr::map but these quite accomplish the goal. I also tried using stringi::stri_detect_regex instead of stringr::str_detect which produced the same results.

Thank you so much for your help!

library(dplyr)
library(tibble)
library(stringr)

favorite_cars <- c("^Merc", "Firebird$")

mtcars <-
  mtcars %>% 
  tibble::rownames_to_column("car")

is_favorite <- function(x) {
  any(stringr::str_detect(x, favorite_cars))
}

# Success: Works on single string
is_favorite("Merc 240D")
#> [1] TRUE
is_favorite("Ferrari Dino")
#> [1] FALSE

# Failure: On vector, returns a single boolean instead of a vector of booleans
is_favorite(mtcars$car)
#> [1] TRUE

# Failure: Add column with single boolean instead of vectorized rowwise
mtcars %>% 
  mutate(fav_car = is_favorite(car)) %>% 
  head()
#>                 car  mpg cyl disp  hp drat    wt  qsec vs am gear carb fav_car
#> 1         Mazda RX4 21.0   6  160 110 3.90 2.620 16.46  0  1    4    4    TRUE
#> 2     Mazda RX4 Wag 21.0   6  160 110 3.90 2.875 17.02  0  1    4    4    TRUE
#> 3        Datsun 710 22.8   4  108  93 3.85 2.320 18.61  1  1    4    1    TRUE
#> 4    Hornet 4 Drive 21.4   6  258 110 3.08 3.215 19.44  1  0    3    1    TRUE
#> 5 Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2    TRUE
#> 6           Valiant 18.1   6  225 105 2.76 3.460 20.22  1  0    3    1    TRUE

# Success...but not ideal
# https://community.rstudio.com/t/vectorise-text-function-for-dplyr-mutate/53387/2
# https://deanattali.com/blog/mutate-non-vectorized/
# https://www.jimhester.com/post/2018-04-12-vectorize/
v_is_favorite <- Vectorize(is_favorite)

mtcars %>% 
  mutate(fav_car = v_is_favorite(car)) %>% 
  head()
#>                 car  mpg cyl disp  hp drat    wt  qsec vs am gear carb fav_car
#> 1         Mazda RX4 21.0   6  160 110 3.90 2.620 16.46  0  1    4    4   FALSE
#> 2     Mazda RX4 Wag 21.0   6  160 110 3.90 2.875 17.02  0  1    4    4   FALSE
#> 3        Datsun 710 22.8   4  108  93 3.85 2.320 18.61  1  1    4    1   FALSE
#> 4    Hornet 4 Drive 21.4   6  258 110 3.08 3.215 19.44  1  0    3    1   FALSE
#> 5 Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2   FALSE
#> 6           Valiant 18.1   6  225 105 2.76 3.460 20.22  1  0    3    1   FALSE

# Success...better but still not ideal
# https://www.jimhester.com/post/2018-04-12-vectorize/
# http://yoshidk6.hatenablog.com/entry/2018/09/05/222248
mtcars %>% 
  mutate(fav_car = purrr::map_lgl(car, is_favorite)) %>% 
  head()
#>                 car  mpg cyl disp  hp drat    wt  qsec vs am gear carb fav_car
#> 1         Mazda RX4 21.0   6  160 110 3.90 2.620 16.46  0  1    4    4   FALSE
#> 2     Mazda RX4 Wag 21.0   6  160 110 3.90 2.875 17.02  0  1    4    4   FALSE
#> 3        Datsun 710 22.8   4  108  93 3.85 2.320 18.61  1  1    4    1   FALSE
#> 4    Hornet 4 Drive 21.4   6  258 110 3.08 3.215 19.44  1  0    3    1   FALSE
#> 5 Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2   FALSE
#> 6           Valiant 18.1   6  225 105 2.76 3.460 20.22  1  0    3    1   FALSE

^{Created on 2020-08-28 by the reprex package (v0.3.0)}

I also consulted the following resources:

Ronak Shah · Accepted Answer

any would always return only one logical value as output. You should collapse your favorite_cars regex as length 1 string.

is_favorite <- function(x) {
  stringr::str_detect(x, paste0(favorite_cars, collapse = "|"))
  #Will also work with base R grepl
  #grepl(paste0(favorite_cars, collapse = "|"), x)
}

and then use :

library(dplyr)
mtcars %>%  mutate(fav_car = is_favorite(car))

#                   car  mpg cyl  disp  hp drat   wt qsec vs am gear carb fav_car
#1            Mazda RX4 21.0   6 160.0 110 3.90 2.62 16.5  0  1    4    4   FALSE
#2        Mazda RX4 Wag 21.0   6 160.0 110 3.90 2.88 17.0  0  1    4    4   FALSE
#3           Datsun 710 22.8   4 108.0  93 3.85 2.32 18.6  1  1    4    1   FALSE
#4       Hornet 4 Drive 21.4   6 258.0 110 3.08 3.21 19.4  1  0    3    1   FALSE
#5    Hornet Sportabout 18.7   8 360.0 175 3.15 3.44 17.0  0  0    3    2   FALSE
#6              Valiant 18.1   6 225.0 105 2.76 3.46 20.2  1  0    3    1   FALSE
#7           Duster 360 14.3   8 360.0 245 3.21 3.57 15.8  0  0    3    4   FALSE
#8            Merc 240D 24.4   4 146.7  62 3.69 3.19 20.0  1  0    4    2    TRUE
#9             Merc 230 22.8   4 140.8  95 3.92 3.15 22.9  1  0    4    2    TRUE
#10            Merc 280 19.2   6 167.6 123 3.92 3.44 18.3  1  0    4    4    TRUE
#11           Merc 280C 17.8   6 167.6 123 3.92 3.44 18.9  1  0    4    4    TRUE
#...
#...

where the pattern that we are looking for becomes

paste0(favorite_cars, collapse = "|")
#[1] "^Merc|Firebird$"

Vectorized function for dplyr::mutate()

Answers (1)

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