R: Extended 'gregexpr' with substring retrieval

gregexpr {microseq}

R Documentation

Extended `gregexpr` with substring retrieval

Description

An extension of the function base::gregexpr enabling retrieval of the matching substrings.

Usage

gregexpr(
  pattern,
  text,
  ignore.case = FALSE,
  perl = FALSE,
  fixed = FALSE,
  useBytes = FALSE,
  extract = FALSE
)

Arguments

`pattern`	Character string containing a regular expression (or character string for `fixed = TRUE`) to be matched in the given character vector. Coerced by `as.character` to a character string if possible. If a character vector of length 2 or more is supplied, the first element is used with a warning. Missing values are not allowed.
`text`	A character vector where matches are sought, or an object which can be coerced by `as.character` to a character vector.
`ignore.case`	If `FALSE`, the pattern matching is case sensitive and if `TRUE`, case is ignored during matching.
`perl`	Logical. Should perl-compatible regexps be used? Has priority over `extended`.
`fixed`	Logical. If `TRUE`, pattern is a string to be matched as is. Overrides all conflicting arguments.
`useBytes`	Logical. If `TRUE` the matching is done byte-by-byte rather than character-by-character. See `grep` for details.
`extract`	Logical indicating if matching substrings should be extracted and returned.

Details

Extended version of base:gregexpr that enables the return of the substrings matching the pattern. The last argument extract is the only difference to base::gregexpr. The default behaviour is identical to base::gregexpr, but setting extract=TRUE means the matching substrings are returned.

Value

It will either return what the base::gregexpr would (extract = FALSE) or a list of substrings matching the pattern (extract = TRUE). There is one list element for each string in text, and each list element contains a character vector of all matching substrings in the corresponding entry of text.

Author(s)

Lars Snipen and Kristian Liland.

Examples

sequences <- c("ACATGTCATGTCC", "CTTGTATGCTG")
gregexpr("ATG", sequences, extract = TRUE)

[Package microseq version 2.0 Index]

Extended gregexpr with substring retrieval