str_subset
Keep strings matching a pattern, or find positions.
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).
Usage
str_subset(string, pattern, negate = FALSE)str_which(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 wantcoll()which respects character matching rules for the specified locale.Match character, word, line and sentence boundaries with
boundary(). An empty pattern, "", is equivalent toboundary("character").- negate
If
TRUE, return non-matching elements.
Details
Vectorised over string and pattern
Value
A character vector.
See Also
grep() with argument value = TRUE,
stringi::stri_subset() for the underlying implementation.
Examples
# NOT RUN {
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"), ".")
# }