gremlr {labelr}

Determine Which Elements of a Character Vector Match at Least One Pattern Contained in Any of the Elements of Another Character Vector

Description

gremlr accepts two character vectors of strings and, for each element of the second vector, determines whether that element matches any of the patterns supplied via any of the elements of the first vector.

Usage

gremlr(patterns, x, ignore.case = TRUE, vals = FALSE)

Arguments

patterns

a character vector of comma-separated, quoted character strings or regular expressions.

x

a character vector that will be tested for presence/absence of the patterns passed via the patterns argument.

ignore.case

search in a non-case-sensitive fashion if TRUE.

vals

by default, vals = FALSE and will return a named vector that indicates, for each unique element of x, whether that x element was a match for any element of patterns (one named logical element returned for each x vector element). If TRUE, vals returns the unique values of x that were matched (one character element for each matched x argument vector element).

Details

This function accepts a character vector of text substring patterns or regular expressions (patterns argument), and searches another character vector (x argument) to determine for each element of x, whether that element is a match (in the sense of base::grepl()) for any pattern element of of patterns. If vals = TRUE (default is FALSE), each matched x element is returned; if vals = FALSE, a vector of named logical values equal in length to x is returned, indicating for each x element whether it contains any text substring or pattern found in any element of patterns (TRUE if so, FALSE if not), with the names corresponding to the elements of the x vector. Used internally by various labelr functions. If ignore.case = TRUE (the default), neither vector is treated case-sensitively (both are coerced to lower-case before other operations).

Used internally by various labelr functions Note that this is the same search and syntax that is performed by greml(gremlr is "greml in reverse"), except that, whereas greml returns matches in terms of the patterns argument, gremlr returns matches in terms of x argument.

Value

a vector, either character (if vals = TRUE) or logical (if vals = FALSE).

Examples

# search for "AB" (case-sensitively) anywhere in subsequent vector
gremlr(c("AB"), c("ab", "ab", "abc", "z"), vals = TRUE, ignore.case = FALSE)
# character(0)

# search for "AB" (non-case-sensitively; the default) anywhere in next vector
gremlr(c("AB"), c("ab", "ab", "abc", "z"), vals = TRUE, ignore.case = TRUE)
# [1] "ab"  "ab"  "abc"

# other searches
gremlr(c("AB"), c("ab", "ab", "abc", "z"), vals = TRUE, ignore.case = FALSE)
gremlr(c("ab"), c("ab", "ab", "abc", "z"), vals = FALSE)
gremlr(c("ab", "Q"), c("ab", "ab", "abc", "z"), vals = FALSE)
gremlr(c("a|b", "Q"), c("a", "b", "abc", "z"), vals = FALSE)
gremlr(c("a|b", "Q"), c("a", "b", "z"), vals = FALSE)
gremlr(c("a|b", "Q"), c("bq", "z"), vals = FALSE)

# compare gremlr (above) to greml() (here)
greml(c("AB"), c("ab", "ab", "abc", "z"), vals = TRUE, ignore.case = FALSE)
greml(c("ab"), c("ab", "ab", "abc", "z"), vals = FALSE)
greml(c("ab", "Q"), c("ab", "ab", "abc", "z"), vals = FALSE)
greml(c("a|b", "Q"), c("a", "b", "abc", "z"), vals = FALSE)
greml(c("a|b", "Q"), c("a", "b", "z"), vals = FALSE)
greml(c("a|b", "Q"), c("bq", "z"), vals = FALSE)