README
¶
String metrics
This library contains implementations of the Levenshtein distance, Jaro-Winkler and Soundex algorithms written in Go (golang). Other algorithms related with string metrics (or string similarity, whatever) are welcome.
- master:
Algorithms
WagnerFischer
func WagnerFischer(a, b string, icost, dcost, scost int) int
The Wagner-Fischer algorithm for calculating the Levenshtein distance. It runs on O(mn) and needs O(2m) space where m is the size of the smallest string. This is kinda optimized so it should be used in most cases.
The first two parameters are the two strings to be compared. The last three parameters are the insertion cost, the deletion cost and the substitution cost. These are normally defined as 1, 1 and 2.
Examples:
smetrics.WagnerFischer("POTATO", "POTATTO", 1, 1, 2)
>> 1, delete the second T on POTATTO
smetrics.WagnerFischer("MOUSE", "HOUSE", 2, 2, 4)
>> 4, substitute M for H
Ukkonen
func Ukkonen(a, b string, icost, dcost, scost int) int
The Ukkonen algorithm for calculating the Levenshtein distance. The algorithm is described here. It runs on O(t . min(m, n)) where t is the actual distance between strings a and b, so this version should be preferred over the WagnerFischer for strings very similar. In practice, it's slower most of the times. It needs O(min(t, m, n)) space.
The first two parameters are the two strings to be compared. The last three parameters are the insertion cost, the deletion cost and the substitution cost. These are normally defined as 1, 1 and 2.
Examples:
smetrics.Ukkonen("POTATO", "POTATTO", 1, 1, 2)
>> 1, delete the second T on POTATTO
smetrics.Ukkonen("MOUSE", "HOUSE", 2, 2, 4)
>> 4, substitute M for H
Jaro
func Jaro(a, b string) float64
The Jaro distance. It is not very accurate, therefore you should prefer the JaroWinkler optimized version.
Examples:
smetrics.Jaro("AL", "AL")
>> 1, equal strings
smetrics.Jaro("MARTHA", "MARHTA")
>> 0.9444444444444445, very likely a typo
smetrics.Jaro("JONES", "JOHNSON")
>> 0.7904761904761904
JaroWinkler
func JaroWinkler(a, b string, boostThreshold float64, prefixSize int) float64
The JaroWinkler distance. JaroWinkler returns a number between 0 and 1 where 1 means perfectly equal and 0 means completely different. It is commonly used on Record Linkage stuff, thus it tries to be accurate for real names and common typos. You should consider it on data such as person names and street names.
JaroWinkler is a more accurate version of the Jaro algorithm. It works by boosting the score of exact matches at the beginning of the strings. By doing this, Winkler says that typos are less common to happen at the beginning. For this to happen, it introduces two more parameters: the boostThreshold and the prefixSize. These are commonly set to 0.7 and 4, respectively.
Examples:
smetrics.JaroWinkler("AL", "AL", 0.7, 4)
>> 1, equal strings
smetrics.JaroWinkler("MARTHA", "MARHTA", 0.7, 4)
>> 0.9611111111111111, very likely a typo
smetrics.JaroWinkler("JONES", "JOHNSON", 0.7, 4)
>> 0.8323809523809523
Soundex
func Soundex(s string) string
The Soundex encoding. It is a phonetic algorithm that considers how the words sound in english. Soundex maps a name to a 4-byte string consisting of the first letter of the original string and three numbers. Strings that sound similar should map to the same thing.
Examples:
smetrics.Soundex("Euler")
>> E460
smetrics.Soundex("Ellery")
>> E460
smetrics.Soundex("Lloyd")
>> L300
smetrics.Soundex("Ladd")
>> L300
Hamming
func Hamming(a, b string) (int, error)
The Hamming distance is simply the minimum number of substitutions required to change one string into the other. Both strings must have the same size, of the function returns an error.
Examples:
smetrics.Hamming("aaa", "aaa")
>> 0, nil
smetrics.Hamming("aaa", "aab")
>> 1, nil
smetrics.Hamming("aaaa", "a")
>> -1, error
TODO
-
Accept cost functions instead of constant values in every Levenshtein implementation.
-
Make a better interface.
-
Moar algos!
Documentation
¶
Overview ¶
String metrics ¶
This library contains implementations of the Levenshtein distance, Jaro-Winkler and Soundex algorithms written in Go (golang). Other algorithms related with string metrics (or string similarity, whatever) are welcome.
Algorithms ¶
## WagnerFischer
func WagnerFischer(a, b string, icost, dcost, scost int) int
The Wagner-Fischer algorithm for calculating the Levenshtein distance. It runs on O(mn) and the currently non-optimized version also needs O(mn) space. This version should be preferred over the Ukkonen one for short strings.
The first two parameters are the two strings to be compared. The last three parameters are the insertion cost, the deletion cost and the substitution cost. These are normally defined as 1, 1 and 2.
#### Examples:
smetrics.WagnerFischer("POTATO", "POTATTO", 1, 1, 2)
>> 1, delete the second T on POTATTO
smetrics.WagnerFischer("MOUSE", "HOUSE", 2, 2, 4)
>> 4, substitute M for H
## Ukkonen
func Ukkonen(a, b string, icost, dcost, scost int) int
The Ukkonen algorithm for calculating the Levenshtein distance. The algorithm is described [here](http://www.cs.helsinki.fi/u/ukkonen/InfCont85.PDF). It runs on O(t . min(m, n)) where t is the actual distance between strings a and b. It needs O(min(t, m, n)) space. This version should be preferred over the WagnerFischer one for very similar strings.
The first two parameters are the two strings to be compared. The last three parameters are the insertion cost, the deletion cost and the substitution cost. These are normally defined as 1, 1 and 2.
#### Examples:
smetrics.Ukkonen("POTATO", "POTATTO", 1, 1, 2)
>> 1, delete the second T on POTATTO
smetrics.Ukkonen("MOUSE", "HOUSE", 2, 2, 4)
>> 4, substitute M for H
## Jaro
func Jaro(a, b string) float64
The Jaro distance. It is not very accurate, therefore you should prefer the JaroWinkler optimized version.
#### Examples:
smetrics.Jaro("AL", "AL")
>> 1, equal strings
smetrics.Jaro("MARTHA", "MARHTA")
>> 0.9444444444444445, very likely a typo
smetrics.Jaro("JONES", "JOHNSON")
>> 0.7904761904761904
## JaroWinkler
func JaroWinkler(a, b string, boostThreshold float64, prefixSize int) float64
The JaroWinkler distance. JaroWinkler returns a number between 0 and 1 where 1 means perfectly equal and 0 means completely different. It is commonly used on Record Linkage stuff, thus it tries to be accurate for real names and common typos. You should consider it on data such as person names and street names.
JaroWinkler is a more accurate version of the Jaro algorithm. It works by boosting the score of exact matches at the beginning of the strings. By doing this, Winkler says that typos are less common to happen at the beginning. For this to happen, it introduces two more parameters: the boostThreshold and the prefixSize. These are commonly set to 0.7 and 4, respectively.
#### Examples:
smetrics.JaroWinkler("AL", "AL", 0.7, 4)
>> 1, equal strings
smetrics.JaroWinkler("MARTHA", "MARHTA", 0.7, 4)
>> 0.9611111111111111, very likely a typo
smetrics.JaroWinkler("JONES", "JOHNSON", 0.7, 4)
>> 0.8323809523809523
## Soundex
func Soundex(s string) string
The Soundex encoding. It is a phonetic algorithm that considers how the words sound in english. Soundex maps a name to a 4-byte string consisting of the first letter of the original string and three numbers. Strings that sound similar should map to the same thing.
#### Examples:
smetrics.Soundex("Euler")
>> E460
smetrics.Soundex("Ellery")
>> E460
smetrics.Soundex("Lloyd")
>> L300
smetrics.Soundex("Ladd")
>> L300
## Hamming
func Hamming(a, b string) (int, error)
The Hamming distance is simply the minimum number of substitutions required to change one string into the other. Both strings must have the same size, of the function returns an error.
#### Examples:
smetrics.Hamming("aaa", "aaa")
>> 0, nil
smetrics.Hamming("aaa", "aab")
>> 1, nil
smetrics.Hamming("aaaa", "a")
>> -1, error
TODO ¶
- Optimize WagnerFischer for memory; currently it stores the whole matrix and so it needs O(mn) space. Only the previous row of the matrix needs to be stored, so it can be easily optimized to use O(m) space.
- Accept cost functions instead of constant values in every Levenshtein implementation.
- Moar algos!
Index ¶
- func Hamming(a, b string) (int, error)
- func Jaro(a, b string) float64
- func JaroRunes(a, b []rune) float64
- func JaroWinkler(a, b string, boostThreshold float64, prefixSize int) float64
- func JaroWinklerRunes(a, b []rune, boostThreshold float64, prefixSize int) float64
- func Soundex(s string) string
- func Ukkonen(a, b string, icost, dcost, scost int) int
- func WagnerFischer(a, b string, icost, dcost, scost int) int
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func JaroWinklerRunes ¶
func WagnerFischer ¶
Types ¶
This section is empty.
Source Files
Directories