R: Approximate String Match Positions

aregexec {utils} | R Documentation

## Approximate String Match Positions

### Description

Determine positions of approximate string matches.

### Usage

    aregexec(pattern, text, max.distance = 0.1, costs = NULL,
             ignore.case = FALSE, fixed = FALSE, useBytes = FALSE)

### Arguments

`pattern` | a non-empty character string or a character string containing a regular expression (for `fixed = FALSE`) to be matched. Coerced by `as.character` to a string if possible.
`text` | character vector where matches are sought. Coerced by `as.character` to a character vector if possible.
`max.distance` | maximum distance allowed for a match. See `agrep`.
`costs` | cost of transformations. See `agrep`.
`ignore.case` | a logical. If `TRUE`, case is ignored for computing the distances.
`fixed` | If `TRUE`, the pattern is matched literally (as is). Otherwise (default), it is matched as a regular expression.
`useBytes` | a logical. If `TRUE` comparisons are byte-by-byte rather than character-by-character.

### Details

`aregexec` provides a different interface to approximate string matching than `agrep` (along the lines of the interfaces to exact string matching provided by `regexec` and `grep`).

Note that by default, `agrep` performs literal matches, whereas `aregexec` performs regular expression matches.

See `agrep` and `adist` for more information about approximate string matching and distances.

Comparisons are byte-by-byte if `pattern` or any element of `text` is marked as `"bytes"`.

### Value

A list of the same length as `text`, each element of which is either -1 if there is no match, or a sequence of integers with the starting positions of the match and all substrings corresponding to parenthesized subexpressions of `pattern`, with attribute `"match.length"` an integer vector giving the lengths of the matches (or -1 for no match).

### See Also

`regmatches` for extracting the matched substrings.

### Examples

    ## Cf. the examples for agrep.
    x <- c("1 lazy", "1", "1 LAZY")
    aregexec("laysy", x, max.distance = 2)
    aregexec("(lay)(sy)", x, max.distance = 2)
    aregexec("(lay)(sy)", x, max.distance = 2, ignore.case = TRUE)
    m <- aregexec("(lay)(sy)", x, max.distance = 2)
    regmatches(x, m)

[Package utils version 3.1.2 Index]