Switch-style recoding of values with string pattern matching

Source: R/grep_case.R

Switch-style recoding of values with string pattern matching

grep_case(
  x,
  ...,
  .preserve = FALSE,
  .default = NA,
  .exhaustive = FALSE,
  preserve = deprecated(),
  default = deprecated()
)

Arguments

x

A vector

...

<dynamic-dots> A sequence of two-sided formulas or named arguments.

  • Formulas: Elements of x that match the regex pattern on the left hand side (LHS) of formulas will be replaced with the value in the right hand side (RHS). The LHS must evaluate to a character string. The RHS must be of length one. NULL inputs are ignored.

  • Named arguments: named arguments are passed to grepl().

.preserve, 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, default

If .preserve is FALSE, a value to replace unmatched elements of x. Defaults to NA.

.exhaustive

If TRUE, unmatched elements of x will result in an error. This can be useful to ensure you aren't accidentally forgetting to recode any values. Defaults to FALSE.

Note that if .preserve is TRUE, .exhaustive will never have any effect.

Value

A vector of the same length as x.

See also

grep_case_fct() to return a factor and grep_case_list() to return a list

fn_case(), to apply a function other than grepl() to each case

switch_case() to recode values with exact matching

in_case(), a pipeable alternative to dplyr::case_when()

switch() and grepl(), which inspired this function

Examples

words <- c("caterpillar", "dogwood", "catastrophe", "dogma")

grep_case(
  words,
  "cat" ~ "feline",
  "dog" ~ "canine"
)
#> [1] "feline" "canine" "feline" "canine"

caps_words <- c("caterpillar", "dogwood", "Catastrophe", "DOGMA")

grep_case(
  caps_words,
  "cat" ~ "feline",
  "dog" ~ "canine",
  ignore.case = TRUE
)
#> [1] "feline" "canine" "feline" "canine"

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

grep_case(
  countries,
  "Deutschland" ~ "Germany",
  "Belgi(qu)?e" ~ "Belgium",
  "Nederland"   ~ "Netherlands",
  "Italia"      ~ "Italy",
  .preserve     = TRUE,
  ignore.case   = TRUE
)
#> [1] "France"      "Germany"     "Germany"     "Netherlands" "Belgium"    
#> [6] "Belgium"     "Luxembourg"  "Italy"