editops's result do not match the ratio's result

ztane / python-Levenshtein

The Levenshtein Python C extension module contains functions for fast computation of Levenshtein distance and string similarity

GNU General Public License v2.0

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editops's result do not match the ratio's result #51

Open brealisty opened 4 years ago

brealisty commented 4 years ago

str1 = 'AB1010' str2 = '1010AB' ratio' result --> 0.6666, that means there are 4 steps（2 delete, 2 insert）,(12-4)/12; editops' result --> [('replace', 0, 0), ('replace', 1, 1), ('replace', 4, 4), ('replace', 5, 5)], obviously, this anwser not match (12-4)/12, instead of (12-8)/12.

some differences in those two function about the edit distance?

BobLd commented 4 years ago

Not sure, but could be linked to an issue in the editops_from_cost_matrix function. Check a possible solution here: https://github.com/ztane/python-Levenshtein/issues/16#issuecomment-613626787

maxbachmann commented 3 years ago

Editops uses the normal uniform Levenshtein distance, while ratio uses the InDel Distance (no Substitutions). In this specific implementation this is achived by giving substitutions a weight of 2 which is similar to a Insertion + a Deletion.