agrep {base}  R Documentation 
Approximate String Matching (Fuzzy Matching)
Description
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).
Usage
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)
Arguments
pattern 
a nonempty character string to be matched. For

x 
character vector where matches are sought.
Coerced by 
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
If 
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 
ignore.case 
if 
value 
if 
fixed 
logical. If 
useBytes 
logical. If 
Details
The Levenshtein edit distance is used as measure of approximateness: it is the (possibly costweighted) total number of insertions, deletions and substitutions required to transform one string into another.
This uses the tre
code by Ville Laurikari
(https://github.com/laurikari/tre), which supports MBCS
character matching.
The main effect of useBytes = TRUE
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
).
Value
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.
Note
Since someone who read the description carelessly even filed a bug
report on it, do note that this matches substrings of each element of
x
(just as grep
does) and not whole
elements. See also adist
in package utils, which
optionally returns the offsets of the matched substrings.
Author(s)
Original version in R < 2.10.0 by David Meyer. Current version by Brian Ripley and Kurt Hornik.
See Also
grep
, adist
.
A different interface to approximate string matching is provided by
aregexec()
.
Examples
agrep("lasy", "1 lazy 2")
agrep("lasy", c(" 1 lazy 2", "1 lasy 2"), max.distance = list(sub = 0))
agrep("laysy", c("1 lazy", "1", "1 LAZY"), max.distance = 2)
agrep("laysy", c("1 lazy", "1", "1 LAZY"), max.distance = 2, value = TRUE)
agrep("laysy", c("1 lazy", "1", "1 LAZY"), max.distance = 2, ignore.case = TRUE)