Case statements applying a function to all inputs

fn_case(x, fn, ..., preserve = FALSE, default = NA)

Arguments

x	A vector
fn	A function to apply to the left-hand side of each formula in `...` Either a quoted or unquoted function name, an anonymous `function`, or a purrr-style formula. The function should take two inputs, the first being `x` and the second being the left-hand side of the formula. The function should return a logical vector, either of length 1 or the same length as `x`.
...	<`dynamic-dots`> A sequence of two-sided formulas or named arguments. Formulas: Elements of `x` that return `TRUE` when passed to `fn` with the left hand side (LHS) of each formula will be replaced with the value in the right hand side (RHS). The LHS must evaluate to a logical vector when passed to `fn` with `x`. The RHS must be of length 1 or the same length as all other RHS. Named arguments: named arguments are passed as additional arguments to the function `fn`.
preserve	If `TRUE`, unmatched elements of `x` will be returned unmodified. (The elements may have their type coerced to be compatible with replacement values.) If `FALSE`, unmatched elements of `x` will be replaced with `default`. Defaults to `FALSE`.
default	If `preserve` is `FALSE`, a value to replace unmatched elements of `x`. Defaults to `NA`.

Value

A vector of length 1 or n, matching the length of the logical input or output vectors. Inconsistent lengths will generate an error.

Examples

# Replicate switch_case()
parties <- sample(c("d", "r", "i", "g", "l"), 20, replace = TRUE)

fn_case(
  parties,
  fn = `%in%`,
  "d" ~ "Democrat",
  "r" ~ "Republican",
  "i" ~ "Independent",
  "g" ~ "Green",
  "l" ~ "Libertarian"
)
#>  [1] "Libertarian" "Green"       "Libertarian" "Green"       "Democrat"   
#>  [6] "Libertarian" "Libertarian" "Libertarian" "Republican"  "Independent"
#> [11] "Independent" "Libertarian" "Libertarian" "Green"       "Libertarian"
#> [16] "Republican"  "Green"       "Republican"  "Independent" "Democrat"   

# Replicate grep_case()
countries <- c(
  "France", "Ostdeutschland", "Westdeutschland", "Nederland",
  "Belgie (Vlaanderen)", "Belgique (Wallonie)", "Luxembourg", "Italia"
)

fn_case(
  countries,
  fn = stringi::stri_detect_regex,
  "Deutschland"    ~ "Germany",
  "Belgi(qu)?e"    ~ "Belgium",
  "Nederland"      ~ "Netherlands",
  "Italia"         ~ "Italy",
  preserve         = TRUE,
  case_insensitive = TRUE
)
#> [1] "France"      "Germany"     "Germany"     "Netherlands" "Belgium"    
#> [6] "Belgium"     "Luxembourg"  "Italy"      

# Recode values in a range
time    <- runif(10, 1, 12)
hours   <- time %/% 1
minutes <- time %% 1 * 60

hours <- hours %>%
  if_case(minutes > 32.5, (. + 1) %% 12, .) %>%
  switch_case(0 ~ 12, preserve = TRUE) %>%
  nombre::cardinal()

minutes %>%
  fn_case(
    fn = ~ abs(.x - .y) <= 2.5,
    0  ~ "o'clock",
    60 ~ "o'clock",
    30 ~ "half past",
    15 ~ "quarter past",
    45 ~ "quarter to",
    5  ~ "five past",
    10 ~ "ten past",
    20 ~ "twenty past",
    25 ~ "twenty-five past",
    55 ~ "five to",
    50 ~ "ten to",
    40 ~ "twenty to",
    35 ~ "twenty-five to"
  ) %>%
  switch_case(
    "o'clock" ~ paste(hours, .),
    default   = paste(., hours)
  )
#>  [1] "twenty-five past eleven" "three o'clock"          
#>  [3] "twenty-five past three"  "half past eight"        
#>  [5] "half past six"           "five past eight"        
#>  [7] "quarter past eight"      "five past two"          
#>  [9] "twenty-five past nine"   "half past nine"

Case statements applying a function to all inputs

Arguments

Value

See also

Examples