# Copyright 2019-2020 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._hassanat.
Hassanat distance
"""
from ._token_distance import _TokenDistance
__all__ = ['Hassanat']
[docs]class Hassanat(_TokenDistance):
r"""Hassanat distance.
For two multisets X and Y drawn from an alphabet S, Hassanat distance
:cite:`Hassanat:2014` is
.. math::
dist_{Hassanat}(X, Y) = \sum_{i \in S} D(X_i, Y_i)
where
.. math::
D(X_i, Y_i) =
\left\{\begin{array}{ll}
1-\frac{1+min(X_i, Y_i)}{1+max(X_i, Y_i)}&,
min(X_i, Y_i) \geq 0
\\
\\
1-\frac{1+min(X_i, Y_i)+|min(X_i, Y_i)|}
{1+max(X_i, Y_i)+|min(X_i, Y_i)|}&,
min(X_i, Y_i) < 0
\end{array}\right.
.. versionadded:: 0.4.0
"""
def __init__(self, tokenizer=None, **kwargs):
"""Initialize Hassanat instance.
Parameters
----------
tokenizer : _Tokenizer
A tokenizer instance from the :py:mod:`abydos.tokenizer` package
**kwargs
Arbitrary keyword arguments
Other Parameters
----------------
qval : int
The length of each q-gram. Using this parameter and tokenizer=None
will cause the instance to use the QGram tokenizer with this
q value.
.. versionadded:: 0.4.0
"""
super(Hassanat, self).__init__(tokenizer=tokenizer, **kwargs)
[docs] def dist_abs(self, src, tar):
"""Return the Hassanat distance of two strings.
Parameters
----------
src : str
Source string (or QGrams/Counter objects) for comparison
tar : str
Target string (or QGrams/Counter objects) for comparison
Returns
-------
float
Hassanat distance
Examples
--------
>>> cmp = Hassanat()
>>> cmp.dist_abs('cat', 'hat')
2.0
>>> cmp.dist_abs('Niall', 'Neil')
3.5
>>> cmp.dist_abs('aluminum', 'Catalan')
7.166666666666667
>>> cmp.dist_abs('ATCG', 'TAGC')
5.0
.. versionadded:: 0.4.0
"""
self._tokenize(src, tar)
distance = 0.0
for tok in self._total().keys():
x = self._src_tokens[tok]
y = self._tar_tokens[tok]
min_val = min(x, y)
if min_val >= 0:
distance += 1 - (1 + min_val) / (1 + max(x, y))
else:
distance += 1 - 1 / (1 + max(x, y) - min_val)
return distance
[docs] def dist(self, src, tar):
"""Return the normalized Hassanat distance of two strings.
Parameters
----------
src : str
Source string (or QGrams/Counter objects) for comparison
tar : str
Target string (or QGrams/Counter objects) for comparison
Returns
-------
float
Normalized Hassanat distance
Examples
--------
>>> cmp = Hassanat()
>>> cmp.dist('cat', 'hat')
0.3333333333333333
>>> cmp.dist('Niall', 'Neil')
0.3888888888888889
>>> cmp.dist('aluminum', 'Catalan')
0.4777777777777778
>>> cmp.dist('ATCG', 'TAGC')
0.5
.. versionadded:: 0.4.0
"""
if src == tar:
return 0.0
return self.dist_abs(src, tar) / len(self._total().keys())
if __name__ == '__main__':
import doctest
doctest.testmod()