labelr (version 0.1.9)

greml: Determine Which Pattern Elements of One Character Vector Are Found in at Least One Element of A Second Character Vector

Description

greml takes two character vectors of strings and, for each pattern represented by an element of the first vector, searches all elements of the second vector to see if any of those elements of the second vector matches that pattern element of the first vector.

Usage

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

Value

a vector, either character (if vals = TRUE) or logical (if 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 patterns, whether a match for that pattern was found somewhere in the x vector (one named logical element returned for each patterns argument vector element). If TRUE, vals returns the unique values of patterns that were matched (one character element for each matched patterns argument vector element).

Details

This function accepts a character vector of text substring patterns or regular expressions (patterns argument), and searches a second character vector (x argument) to determine which elements of the first vector (patterns) match at least one element anywhere in the second vector (x). If vals = TRUE (default is FALSE), each matched pattern element is returned; if vals = FALSE, a vector of named logical values equal in length to the object supplied to the patterns argument is returned, indicating for each patterns element whether a match for it was found anywhere in x (TRUE if so, FALSE if not), with the names corresponding to the elements of the patterns vector. If ignore.case = TRUE (the default), neither vector is treated case- sensitively (both are coerced to lower-case before other operations occur).

Used internally by various labelr functions (e.g., use_val_labs). Note that this is the same search and syntax that is performed by gremlr() (gremlr means "greml in reverse"), except that, whereas greml returns matches in terms of the patterns argument (i.e., which patterns elements match at least one x element), gremlr returns matches in terms of the x argument.

Examples

# search for "AB" (case-sensitively) anywhere in subsequent vector
greml(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
greml(c("AB"), c("ab", "ab", "abc", "z"), vals = TRUE, ignore.case = TRUE)
# [1] "AB"

# other searches
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)
greml(c("a|b", "Q"), c("bq", "z"), vals = TRUE)

# compare greml (above) to gremlr() (here)
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)