# Copyright 2018-2020 by Christopher C. Little.
# This file is part of Abydos.
#
# Abydos is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Abydos is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Abydos. If not, see <http://www.gnu.org/licenses/>.
"""abydos.distance._ozbay.
Ozbay metric
"""
from . import Jaccard, LCSstr, Levenshtein
from ._distance import _Distance
from ..tokenizer import QGrams
__all__ = ['Ozbay']
[docs]class Ozbay(_Distance):
"""Ozbay metric.
The Ozbay metric :cite:`Ozbay:2015` is a string distance measure developed
by Hakan Ozbay, which combines Jaccard distance, Levenshtein distance, and
longest common substring distance.
The normalized variant should be considered experimental.
.. versionadded:: 0.4.0
"""
_lev = Levenshtein()
_jac = Jaccard(tokenizer=QGrams(qval=1, start_stop='', scaler='set'))
_lcs = LCSstr()
[docs] def dist_abs(self, src, tar):
"""Return the Ozbay metric.
Parameters
----------
src : str
Source string for comparison
tar : str
Target string for comparison
Returns
-------
float
Ozbay metric
Examples
--------
>>> cmp = Ozbay()
>>> round(cmp.dist_abs('cat', 'hat'), 12)
0.75
>>> round(cmp.dist_abs('Niall', 'Neil'), 12)
6.0
>>> round(cmp.dist_abs('Colin', 'Cuilen'), 12)
7.714285714286
>>> cmp.dist_abs('ATCG', 'TAGC')
3.0
.. versionadded:: 0.4.0
"""
lev_dist = self._lev.dist_abs(src, tar)
lev_metric = 0.0 if lev_dist == 0 else lev_dist / len(src)
jac_metric = self._jac.dist_abs(src, tar)
lcs_metric = self._lcs.sim(src, tar)
if jac_metric == 1.0:
ozbay_metric = lev_dist
elif jac_metric == 0.0:
ozbay_metric = lev_metric
else:
ozbay_metric = jac_metric * lev_dist
if lcs_metric > 0.0:
ozbay_metric /= lcs_metric
else:
ozbay_metric *= min(len(src), len(tar))
return ozbay_metric
[docs] def dist(self, src, tar):
"""Return the normalized Ozbay distance.
Parameters
----------
src : str
Source string for comparison
tar : str
Target string for comparison
Returns
-------
float
Normalized Ozbay distance
Examples
--------
>>> cmp = Ozbay()
>>> round(cmp.dist('cat', 'hat'), 12)
0.027777777778
>>> round(cmp.dist('Niall', 'Neil'), 12)
0.24
>>> round(cmp.dist('Colin', 'Cuilen'), 12)
0.214285714286
>>> cmp.dist('ATCG', 'TAGC')
0.140625
.. versionadded:: 0.4.0
"""
dist = self.dist_abs(src, tar)
if dist:
return dist / (len(src) * len(tar) / self._lcs.dist(src, tar))
return dist
if __name__ == '__main__':
import doctest
doctest.testmod()