Find matching indices — str

str_which() returns the indices of string where there's at least one match to pattern. It's a wrapper around which(str_detect(x, pattern)), and is equivalent to grep(pattern, x).

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 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

An integer vector, usually smaller than string.

Examples

fruit <- c("apple", "banana", "pear", "pineapple")
str_which(fruit, "a")
#> [1] 1 2 3 4

# Elements that don't match
str_which(fruit, "^p", negate = TRUE)
#> [1] 1 2

# Missings never match
str_which(c("a", NA, "b"), ".")
#> [1] 1 3