str_subset() is a wrapper around x[str_detect(x, pattern)],
and is equivalent to grep(pattern, x, value = TRUE).
str_which() is a wrapper around which(str_detect(x, pattern)),
and is equivalent to grep(pattern, x).
See str_detect() for an equivalent to grepl(pattern, x).
str_subset(string, pattern, negate = FALSE)str_which(string, pattern, negate = FALSE)
A character vector.
Input vector. Either a character vector, or something coercible to one.
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").
If TRUE, return non-matching elements.
Vectorised over string and pattern
grep() with argument value = TRUE,
stringi::stri_subset() for the underlying implementation.
fruit <- c("apple", "banana", "pear", "pinapple")
str_subset(fruit, "a")
str_which(fruit, "a")
str_subset(fruit, "^a")
str_subset(fruit, "a$")
str_subset(fruit, "b")
str_subset(fruit, "[aeiou]")
# Returns elements that do NOT match
str_subset(fruit, "^p", negate = TRUE)
# Missings never match
str_subset(c("a", NA, "b"), ".")
str_which(c("a", NA, "b"), ".")
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