/* # 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! */ package smetrics