如何解决dplyr :: mutate
我正在尝试编写一个 vectorized函数，以将字符串与正则表达式的向量进行比较，如果字符串与任何正则表达式匹配，则返回TRUE。该函数应在单个字符串，字符串向量以及dplyr::mutate内工作。我在对函数进行矢量化时遇到了麻烦。在下面的reprex中，我要向量化的函数是is_favorite。我提出了使用base::Vectorize和purrr::map的变通方法，但是这些变通方法确实达到了目标。我还尝试使用stringi::stri_detect_regex代替stringr::str_detect来产生相同的结果。
非常感谢您的帮助！
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
由reprex package（v0.3.0）于2020-08-28创建
我还参考了以下资源：
- https://adv-r.hadley.nz/perf-improve.html#vectorise
- https://deanattali.com/blog/mutate-non-vectorized/
- https://www.jimhester.com/post/2018-04-12-vectorize/
- https://community.rstudio.com/t/vectorise-text-function-for-dplyr-mutate/53387/2
- http://yoshidk6.hatenablog.com/entry/2018/09/05/222248
- https://dplyr.tidyverse.org/articles/programming.html
解决方法
any将始终仅返回一个逻辑值作为输出。您应该将favorite_cars正则表达式折叠为长度为1的字符串。
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)
}
然后使用：
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
#...
#...
我们要寻找的模式变为
paste0(favorite_cars,collapse = "|")
#[1] "^Merc|Firebird$"
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