case_match with factor levels — case_match

Recode a variable using the dplyr::case_match() syntax

Usage

case_match_fct(.x, ..., .default = NULL)

Arguments

.x

A vector to match against.

...

<dynamic-dots> A sequence of two-sided formulas: old_values ~ new_value. The right hand side (RHS) determines the output value for all values of .x that match the left hand side (LHS).

The LHS must evaluate to the same type of vector as .x. It can be any length, allowing you to map multiple .x values to the same RHS value. If a value is repeated in the LHS, i.e. a value in .x matches to multiple cases, the first match is used.

The RHS inputs will be coerced to their common type. Each RHS input will be recycled to the size of .x.

.default

The value used when values in .x aren't matched by any of the LHS inputs. If NULL, the default, a NA will be used.

Examples

# import dplyr so we can use their starwars dataset
library(dplyr)
#> 
#> Attaching package: ‘dplyr’
#> The following objects are masked from ‘package:stats’:
#> 
#>     filter, lag
#> The following objects are masked from ‘package:base’:
#> 
#>     intersect, setdiff, setequal, union
# create a vector with a variable label
species <- starwars$species %>% structure(label = "This is a variable label")

new_species <- case_match_fct(
  species,
  "Human" ~ "Humanoid",
  "Droid" ~ "Robot",
  c("Wookiee", "Ewok") ~ "Hairy",
  .default = "Other"
)

# now let's check to see that it added the transformation metadata and the
#variable label
str(new_species)
#>  Factor w/ 4 levels "Humanoid","Robot",..: 1 2 2 1 1 1 1 2 1 1 ...
#>  - attr(*, "label")= chr "This is a variable label"
#>  - attr(*, "transformation")= 'glue' chr "Recoded 'species' as a factor and set the levels based on their order.\nThe data transformation is as follows:\"| __truncated__

# now let's create a variable "new_species" and get the frequencies for it
# we can see the frequencies are in the same order we applied.
starwars %>%
  dplyr::mutate(
    new_species = case_match_fct(
      species,
      "Human" ~ "Humanoid",
      "Droid" ~ "Robot",
      c("Wookiee", "Ewok") ~ "Hairy",
      .default = "Other"
    )
  ) %>%
  dplyr::count(new_species)
#> # A tibble: 4 × 2
#>   new_species     n
#>   <fct>       <int>
#> 1 Humanoid       35
#> 2 Robot           6
#> 3 Hairy           3
#> 4 Other          43

# now let's do the same but with dplyr::case_match()
# we can see that the frequencies are in alphabetical order
starwars %>%
  dplyr::mutate(
    new_species = dplyr::case_match(
      species,
      "Human" ~ "Humanoid",
      "Droid" ~ "Robot",
      c("Wookiee", "Ewok") ~ "Hairy",
      .default = "Other"
    )
  ) %>%
  dplyr::count(new_species)
#> # A tibble: 4 × 2
#>   new_species     n
#>   <chr>       <int>
#> 1 Hairy           3
#> 2 Humanoid       35
#> 3 Other          43
#> 4 Robot           6