str_detect

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Detect the presence or absence of a pattern in a string.

Vectorised over string and pattern. Equivalent to grepl(pattern, x). See str_which() for an equivalent to grep(pattern, x).

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 stringi::stringi-search-regex. Control options with regex().

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, return non-matching elements.

Value

A logical vector.

See Also

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

Aliases
  • str_detect
Examples
# NOT RUN {
fruit <- c("apple", "banana", "pear", "pinapple")
str_detect(fruit, "a")
str_detect(fruit, "^a")
str_detect(fruit, "a$")
str_detect(fruit, "b")
str_detect(fruit, "[aeiou]")

# Also vectorised over pattern
str_detect("aecfg", letters)

# Returns TRUE if the pattern do NOT match
str_detect(fruit, "^p", negate = TRUE)
# }
Documentation reproduced from package stringr, version 1.4.0, License: GPL-2 | file LICENSE

Community examples

antoine.fabri@gmail.com at Jun 13, 2018 stringr v1.3.1

comparison with `grepl`: `str_detect` behaves the same as `grepl` if we use only 2 first arguments (i.e. if we keep all optional parameters as default for `grepl`). These 2 first arguments are switched however. ```r fruit <- c("apple", "banana", "pear", "pinapple") # [1] TRUE identical(str_detect(fruit, "a"), grepl("a",fruit)) # [1] TRUE identical(str_detect(fruit, "^a"), grepl("^a",fruit)) # [1] TRUE identical(str_detect(fruit, "a$"), grepl("a$",fruit)) # [1] TRUE identical(str_detect(fruit, "b"), grepl("b",fruit)) # [1] TRUE identical(str_detect(fruit, "[aeiou]"), grepl("[aeiou]",fruit)) # [1] TRUE ``` An additional feature of `str_detect` is that it is vectorized over the `pattern` argument: ``` str_detect("aecfg", letters) grepl(letters,"aecfg") # [1] TRUE # Warning message: # In grepl(letters, "aecfg") : # argument 'pattern' has length > 1 and only the first element will be used identical(str_detect("aecfg", letters), Vectorize(grepl,"pattern", USE.NAMES=FALSE)(letters,"aecfg")) # [1] TRUE ```

kirannbishwa01@gmail.com at Aug 20, 2017 stringr v1.1.0

ex01 = data.frame(fruits = c("apple", "apple", "orange", "banana", "orange", "orange", "banana", "apple"), taste = c("sweet", "tarty", "tangy", "sweet", "tangy", "tangy", "sweet", "sweet"), qty = c(3, 2, 3, 2, 4, 1, 6, 2)) #### to select using string matches - the sweet ones ex01[str_detect(ex01$taste, "swe"), ]

kirannbishwa01@gmail.com at Aug 20, 2017 stringr v1.1.0

ex01 = data.frame(fruits = c("apple", "apple", "orange", "banana", "orange", "orange", "banana", "apple"), taste = c("sweet", "tarty", "tangy", "sweet", "tangy", "tangy", "sweet", "sweet"), qty = c(3, 2, 3, 2, 4, 1, 6, 2)) #### to select using string matches - the sweet ones ex01[str_detect(ex01$taste, "swe"), ]

kirannbishwa01@gmail.com at Aug 20, 2017 stringr v1.1.0

ex01 = data.frame(fruits = c("apple", "apple", "orange", "banana", "orange", "orange", "banana", "apple"), taste = c("sweet", "tarty", "tangy", "sweet", "tangy", "tangy", "sweet", "sweet"), qty = c(3, 2, 3, 2, 4, 1, 6, 2)) #### to select using string matches - the sweet ones ex01[str_detect(ex01$taste, "swe"), ]