An implementation of Jaro-Winkler distance algorithm, it's a C extension and will fallback to pure Ruby version in JRuby. Both of them supports UTF-8 string.

Installation

gem install jaro_winkler

Usage

require 'jaro_winkler'

# Jaro Winkler Distance

JaroWinkler.distance "MARTHA", "MARHTA"
# => 0.9611
JaroWinkler.distance "MARTHA", "marhta", ignore_case: true
# => 0.9611
JaroWinkler.distance "MARTHA", "MARHTA", weight: 0.2
# => 0.9778

# Jaro Distance

JaroWinkler.jaro_distance "MARTHA", "MARHTA"
# => 0.9444444444444445

There is no JaroWinkler.jaro_winkler_distance, it's tediously long.

Options

Name	Type	Default	Note
ignore_case	boolean	false	All lower case characters are converted to upper case prior to the comparison.
weight	number	0.1	A constant scaling factor for how much the score is adjusted upwards for having common prefixes.
threshold	number	0.7	The prefix bonus is only added when the compared strings have a Jaro distance above the threshold.
adj_table	boolean	false	The option is used to give partial credit for characters that may be errors due to known phonetic or character recognition errors. A typical example is to match the letter "O" with the number "0".

Adjusting Table

Default Table

['A', 'E'], ['A', 'I'], ['A', 'O'], ['A', 'U'], ['B', 'V'], ['E', 'I'], ['E', 'O'], ['E', 'U'], ['I', 'O'], ['I', 'U'],
['O', 'U'], ['I', 'Y'], ['E', 'Y'], ['C', 'G'], ['E', 'F'], ['W', 'U'], ['W', 'V'], ['X', 'K'], ['S', 'Z'], ['X', 'S'],
['Q', 'C'], ['U', 'V'], ['M', 'N'], ['L', 'I'], ['Q', 'O'], ['P', 'R'], ['I', 'J'], ['2', 'Z'], ['5', 'S'], ['8', 'B'],
['1', 'I'], ['1', 'L'], ['0', 'O'], ['0', 'Q'], ['C', 'K'], ['G', 'J'], ['E', ' '], ['Y', ' '], ['S', ' ']

How it works?

Original Formula:

where

m is the number of matching characters.
t is half the number of transpositions.

With Adjusting Table:

where

s is the number of nonmatching but similar characters.

Why This?

There is also another similar gem named fuzzy-string-match which both provides C and Ruby version as well.

I reinvent this wheel because of the naming in fuzzy-string-match such as getDistance breaks convention, and some weird code like a1 = s1.split( // ) (s1.chars could be better), furthermore, it's bugged (see tables below).

Compare with other gems

            | jaro_winkler | fuzzystringmatch | hotwater    | amatch

--------------- | ------------ | ---------------- | -------- | ------ UTF-8 Suport | Yes | Pure Ruby only | No | No Windows Support | Yes | | No | Yes Adjusting Table | Yes | No | No | No Native | Yes | Yes | Yes | Yes Pure Ruby | Yes | Yes | No | No Speed | Medium | Fast | Medium | Slow

I made a table below to compare accuracy between each gem:

str_1	str_2	origin	jaro_winkler	fuzzystringmatch	hotwater	amatch
"henka"	"henkan"	0.9667	0.9667	0.9722	0.9667	0.9444
"al"	"al"	1.0	1.0	1.0	1.0	1.0
"martha"	"marhta"	0.9611	0.9611	0.9611	0.9611	0.9444
"jones"	"johnson"	0.8324	0.8324	0.8324	0.8324	0.7905
"abcvwxyz"	"cabvwxyz"	0.9583	0.9583	0.9583	0.9583	0.9583
"dwayne"	"duane"	0.84	0.84	0.84	0.84	0.8222
"dixon"	"dicksonx"	0.8133	0.8133	0.8133	0.8133	0.7667
"fvie"	"ten"	0.0	0.0	0.0	0.0	0.0

The "origin" result is from the original C implementation by the author of the algorithm.
Test data are borrowed from fuzzy-string-match's rspec file.

Benchmark

$ bundle exec rake benchmark
2015-12-12 20:37:34 UTC

# C Extension
Rehearsal ----------------------------------------------------------
jaro_winkler 1.4.0       0.340000   0.000000   0.340000 (  0.345071)
fuzzystringmatch 0.9.7   0.470000   0.000000   0.470000 (  0.467571)
hotwater 0.1.2           0.380000   0.000000   0.380000 (  0.382495)
amatch 0.3.0             1.020000   0.010000   1.030000 (  1.032459)
------------------------------------------------- total: 2.220000sec

                             user     system      total        real
jaro_winkler 1.4.0       0.350000   0.000000   0.350000 (  0.354300)
fuzzystringmatch 0.9.7   0.480000   0.000000   0.480000 (  0.480397)
hotwater 0.1.2           0.400000   0.000000   0.400000 (  0.396380)
amatch 0.3.0             1.030000   0.000000   1.030000 (  1.028923)

# Pure Ruby
Rehearsal ----------------------------------------------------------
jaro_winkler 1.4.0       0.680000   0.010000   0.690000 (  0.690518)
fuzzystringmatch 0.9.7   1.610000   0.000000   1.610000 (  1.608468)
------------------------------------------------- total: 2.300000sec

                             user     system      total        real
jaro_winkler 1.4.0       0.620000   0.000000   0.620000 (  0.619257)
fuzzystringmatch 0.9.7   1.600000   0.010000   1.610000 (  1.597612)

Todo

Custom adjusting word table.

johnlinvc/jaro_winkler