Find matching observations across vectors

vec_in() returns a logical vector based on whether needle is found in haystack. vec_match() returns an integer vector giving location of needle in haystack, or NA if it's not found.

vec_match(
  needles,
  haystack,
  ...,
  na_equal = TRUE,
  needles_arg = "",
  haystack_arg = ""
)

vec_in(
  needles,
  haystack,
  ...,
  na_equal = TRUE,
  needles_arg = "",
  haystack_arg = ""
)

Arguments

needles, haystack

Vector of needles to search for in vector haystack. haystack should usually be unique; if not vec_match() will only return the location of the first match.

needles and haystack are coerced to the same type prior to comparison.

...

These dots are for future extensions and must be empty.

na_equal

If TRUE, missing values in needles can be matched to missing values in haystack. If FALSE, they propagate, missing values in needles are represented as NA in the return value.

needles_arg, haystack_arg

Argument tags for needles and haystack used in error messages.

Value

A vector the same length as needles. vec_in() returns a logical vector; vec_match() returns an integer vector.

Details

vec_in() is equivalent to %in%; vec_match() is equivalent to match().

Missing values

In most cases places in R, missing values are not considered to be equal, i.e. NA == NA is not TRUE. The exception is in matching functions like match() and merge(), where an NA will match another NA. By vec_match() and vec_in() will match NAs; but you can control this behaviour with the na_equal argument.

Dependencies

• vec_cast_common() with fallback

• vec_proxy_equal()

Examples

hadley <- strsplit("hadley", "")[[1]]
vec_match(hadley, letters)
#> [1]  8  1  4 12  5 25

vowels <- c("a", "e", "i", "o", "u")
vec_match(hadley, vowels)
#> [1] NA  1 NA NA  2 NA
vec_in(hadley, vowels)
#> [1] FALSE  TRUE FALSE FALSE  TRUE FALSE

# Only the first index of duplicates is returned
vec_match(c("a", "b"), c("a", "b", "a", "b"))
#> [1] 1 2