Detect the presence/absence of a match

str_detect() returns a logical vector with TRUE for each element of string that matches pattern and FALSE otherwise. It's equivalent to grepl(pattern, string).

Usage

str_detect(string, pattern, negate = FALSE)

Arguments

string

Input vector. Either a character vector, or something coercible to one.

pattern

Pattern to look for.

The default interpretation is a regular expression, as described in vignette("regular-expressions"). Use regex() for finer control of the matching behaviour.

Match a fixed string (i.e. by comparing only bytes), using fixed(). This is fast, but approximate. Generally, for matching human text, you'll want coll() which respects character matching rules for the specified locale.

Match character, word, line and sentence boundaries with boundary(). An empty pattern, "", is equivalent to boundary("character").

negate

If TRUE, inverts the resulting boolean vector.

Value

A logical vector the same length as string/pattern.

See also

stringi::stri_detect() which this function wraps, str_subset() for a convenient wrapper around x[str_detect(x, pattern)]

Examples

fruit <- c("apple", "banana", "pear", "pineapple")
str_detect(fruit, "a")
#> [1] TRUE TRUE TRUE TRUE
str_detect(fruit, "^a")
#> [1]  TRUE FALSE FALSE FALSE
str_detect(fruit, "a$")
#> [1] FALSE  TRUE FALSE FALSE
str_detect(fruit, "b")
#> [1] FALSE  TRUE FALSE FALSE
str_detect(fruit, "[aeiou]")
#> [1] TRUE TRUE TRUE TRUE

# Also vectorised over pattern
str_detect("aecfg", letters)
#>  [1]  TRUE FALSE  TRUE FALSE  TRUE  TRUE  TRUE FALSE FALSE FALSE FALSE
#> [12] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
#> [23] FALSE FALSE FALSE FALSE

# Returns TRUE if the pattern do NOT match
str_detect(fruit, "^p", negate = TRUE)
#> [1]  TRUE  TRUE FALSE FALSE