README.md
In RLesur/casewhen: Create Reusable 'dplyr' 'case_when()' Functions

casewhen

The goal of casewhen is to create reusable dplyr::case_when() functions. SAS users may recognise a behavior close to the SAS FORMATS.

You can install the development version from GitHub with:

# install.packages("devtools")
devtools::install_github("RLesur/casewhen")

During data wrangling with dplyr, one may use several times identical case_when() clauses in different steps. This can lead to a non-DRY code. This package provides a convenient mean to define and reuse dplyr::case_when() functions.

With casewhen, you can easily create reusable dplyr::case_when() functions with the function create_case_when():

library(dplyr)
library(casewhen)

people <- tribble(
  ~name, ~sex, ~seek,
  "Mary", "F", "M",
  "Henry", "M", "F"
)

cw_sex <- create_case_when(
  x == "F" ~ "Woman",
  x == "M" ~ "Man",
  TRUE ~ as.character(x),
  vars = "x"
)

people %>% 
  mutate(sex_label = cw_sex(sex), 
         seek_label = cw_sex(seek))
#> # A tibble: 2 x 5
#>   name  sex   seek  sex_label seek_label
#>   <chr> <chr> <chr> <chr>     <chr>     
#> 1 Mary  F     M     Woman     Man       
#> 2 Henry M     F     Man       Woman

Reusing a case_when() function is mainly convenient when the same transformation is performed across different datasets.

cw_sexyverse <- create_case_when(
  x == "F" | x == "female" & y == "Human" ~ "Woman",
  x == "M" | x == "male" & y == "Human" ~ "Man",
  TRUE ~ as.character(x),
  vars = c("x", "y")
)

people %>% 
  mutate(sex_label = cw_sexyverse(sex, "Human"))
#> # A tibble: 2 x 4
#>   name  sex   seek  sex_label
#>   <chr> <chr> <chr> <chr>    
#> 1 Mary  F     M     Woman    
#> 2 Henry M     F     Man

starwars %>%
  mutate(sex_label = cw_sexyverse(gender, species)) %>%
  select(name, gender, species, sex_label) %>%
  head()
#> # A tibble: 6 x 4
#>   name           gender species sex_label
#>   <chr>          <chr>  <chr>   <chr>    
#> 1 Luke Skywalker male   Human   Man      
#> 2 C-3PO          <NA>   Droid   <NA>     
#> 3 R2-D2          <NA>   Droid   <NA>     
#> 4 Darth Vader    male   Human   Man      
#> 5 Leia Organa    female Human   Woman    
#> 6 Owen Lars      male   Human   Man

`dbplyr` support

You only have to register the case_when functions to your connection:

con <- 
  DBI::dbConnect(RSQLite::SQLite(), ":memory:") %>%
  add_case_when(cw_sex, cw_sexyverse)

people_db <- copy_to(con, people)
starwars_db <- copy_to(con, starwars %>% select(name, gender, species))

people_db %>% 
  mutate(sex_label = cw_sex(sex), 
         seek_label = cw_sex(seek)) %>%
  show_query()

<SQL>

SELECT `name`, `sex`, `seek`, 
    CASE
      WHEN (`sex` = 'F') THEN ('Woman')
      WHEN (`sex` = 'M') THEN ('Man')
      WHEN (1) THEN (CAST(`sex` AS TEXT))
    END AS `sex_label`, 
    CASE
      WHEN (`seek` = 'F') THEN ('Woman')
      WHEN (`seek` = 'M') THEN ('Man')
      WHEN (1) THEN (CAST(`seek` AS TEXT))
    END AS `seek_label`
FROM `people`

people_db %>%
  mutate(sex_label = cw_sexyverse(sex, "Human")) %>%
  show_query()

<SQL>

SELECT `name`, `sex`, `seek`, 
    CASE
      WHEN (`sex` = 'F' OR `sex` = 'female' AND 'Human' = 'Human') THEN ('Woman')
      WHEN (`sex` = 'M' OR `sex` = 'male' AND 'Human' = 'Human') THEN ('Man')
      WHEN (1) THEN (CAST(`sex` AS TEXT))
    END AS `sex_label`
FROM `people`

starwars_db %>%
  mutate(sex_label = cw_sexyverse(gender, species)) %>%
  show_query()

<SQL>

SELECT `name`, `gender`, `species`, 
    CASE
      WHEN (`gender` = 'F' OR `gender` = 'female' AND `species` = 'Human') THEN ('Woman')
      WHEN (`gender` = 'M' OR `gender` = 'male' AND `species` = 'Human') THEN ('Man')
      WHEN (1) THEN (CAST(`gender` AS TEXT))
    END AS `sex_label`
FROM `starwars %>% select(name, gender, species)`