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)

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

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 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"