case_when

A general vectorised if

This function allows you to vectorise multiple if and else if statements. It is an R equivalent of the SQL CASE WHEN statement.

Usage

case_when(...)

Aliases

• case_when

Examples

# NOT RUN {
x <- 1:50
case_when(
  x %% 35 == 0 ~ "fizz buzz",
  x %% 5 == 0 ~ "fizz",
  x %% 7 == 0 ~ "buzz",
  TRUE ~ as.character(x)
)

# Like an if statement, the arguments are evaluated in order, so you must
# proceed from the most specific to the most general. This won't work:
case_when(
  TRUE ~ as.character(x),
  x %%  5 == 0 ~ "fizz",
  x %%  7 == 0 ~ "buzz",
  x %% 35 == 0 ~ "fizz buzz"
)

# All RHS values need to be of the same type. Inconsistent types will throw an error.
# This applies also to NA values used in RHS: NA is logical, use
# typed values like NA_real_, NA_complex, NA_character_, NA_integer_ as appropriate.
case_when(
  x %% 35 == 0 ~ NA_character_,
  x %% 5 == 0 ~ "fizz",
  x %% 7 == 0 ~ "buzz",
  TRUE ~ as.character(x)
)
case_when(
  x %% 35 == 0 ~ 35,
  x %% 5 == 0 ~ 5,
  x %% 7 == 0 ~ 7,
  TRUE ~ NA_real_
)
# This throws an error as NA is logical not numeric
# }
# NOT RUN {
case_when(
  x %% 35 == 0 ~ 35,
  x %% 5 == 0 ~ 5,
  x %% 7 == 0 ~ 7,
  TRUE ~ NA
)
# }
# NOT RUN {
# case_when is particularly useful inside mutate when you want to
# create a new variable that relies on a complex combination of existing
# variables
starwars %>%
  select(name:mass, gender, species) %>%
  mutate(
    type = case_when(
      height > 200 | mass > 200 ~ "large",
      species == "Droid"        ~ "robot",
      TRUE                      ~  "other"
    )
  )

# Dots support splicing:
patterns <- list(
  x %% 35 == 0 ~ "fizz buzz",
  x %% 5 == 0 ~ "fizz",
  x %% 7 == 0 ~ "buzz",
  TRUE ~ as.character(x)
)
case_when(!!!patterns)
# }