Searches for approximate matches to `pattern`

(the first argument)
within each element of the string `x`

(the second argument) using
the generalized Levenshtein edit distance (the minimal possibly
weighted number of insertions, deletions and substitutions needed to
transform one string into another).

```
agrep(pattern, x, max.distance = 0.1, costs = NULL,
ignore.case = FALSE, value = FALSE, fixed = TRUE,
useBytes = FALSE)
```agrepl(pattern, x, max.distance = 0.1, costs = NULL,
ignore.case = FALSE, fixed = TRUE, useBytes = FALSE)

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.

x

character vector where matches are sought.
Coerced by `as.character`

to a character vector if
possible.

max.distance

Maximum distance allowed for a match. Expressed
either as integer, or as a fraction of the *pattern* length
times the maximal transformation cost (will be replaced by the
smallest integer not less than the corresponding fraction), or a
list with possible components

`cost`

:maximum number/fraction of match cost (generalized Levenshtein distance)

`all`

:maximal number/fraction of

*all*transformations (insertions, deletions and substitutions)`insertions`

:maximum number/fraction of insertions

`deletions`

:maximum number/fraction of deletions

`substitutions`

:maximum number/fraction of substitutions

If `cost`

is not given, `all`

defaults to 10%, and the
other transformation number bounds default to `all`

.
The component names can be abbreviated.

costs

a numeric vector or list with names partially matching
`insertions`, `deletions` and `substitutions` giving
the respective costs for computing the generalized Levenshtein
distance, or `NULL`

(default) indicating using unit cost for
all three possible transformations.
Coerced to integer via `as.integer`

if possible.

ignore.case

if `FALSE`

, the pattern matching is *case
sensitive* and if `TRUE`

, case is ignored during matching.

value

if `FALSE`

, a vector containing the (integer)
indices of the matches determined is returned and if `TRUE`

, a
vector containing the matching elements themselves is returned.

fixed

logical. If `TRUE`

(default), the pattern is
matched literally (as is). Otherwise, it is matched as a regular
expression.

useBytes

logical. in a multibyte locale, should the comparison be character-by-character (the default) or byte-by-byte.

`agrep`

returns a vector giving the indices of the elements that
yielded a match, or, if `value`

is `TRUE`

, the matched
elements (after coercion, preserving names but no other attributes).

`agrepl`

returns a logical vector.

The Levenshtein edit distance is used as measure of approximateness: it is the (possibly cost-weighted) total number of insertions, deletions and substitutions required to transform one string into another.

This uses `tre`

by Ville Laurikari
(http://laurikari.net/tre/), which supports MBCS
character matching.

The main effect of `useBytes`

is to avoid errors/warnings about
invalid inputs and spurious matches in multibyte locales.
It inhibits the conversion of inputs with marked encodings, and is
forced if any input is found which is marked as `"bytes"`

(see
`Encoding`

).

```
agrep("lasy", "1 lazy 2")
agrep("lasy", c(" 1 lazy 2", "1 lasy 2"), max = list(sub = 0))
agrep("laysy", c("1 lazy", "1", "1 LAZY"), max = 2)
agrep("laysy", c("1 lazy", "1", "1 LAZY"), max = 2, value = TRUE)
agrep("laysy", c("1 lazy", "1", "1 LAZY"), max = 2, ignore.case = TRUE)
```

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