# 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._unigram_subtuple.
Unigram subtuple similarity
"""
from math import log
from ._token_distance import _TokenDistance
__all__ = ['UnigramSubtuple']
[docs]class UnigramSubtuple(_TokenDistance):
r"""Unigram subtuple similarity.
For two sets X and Y and a population N, unigram subtuple similarity
:cite:`Pecina:2010` is
.. math::
sim_{unigram~subtuple}(X, Y) =
log(\frac{|X \cap Y| \cdot |(N \setminus X) \setminus Y|}
{|X \setminus Y| \cdot |Y \setminus Y|}) - 3.29 \cdot
\sqrt{\frac{1}{|X \cap Y|} + \frac{1}{|X \setminus Y|} +
\frac{1}{|Y \setminus X|} +
\frac{1}{|(N \setminus X) \setminus Y|}}
In :ref:`2x2 confusion table terms <confusion_table>`, where a+b+c+d=n,
this is
.. math::
sim_{unigram~subtuple} =
log(\frac{ad}{bc}) - 3.29 \cdot
\sqrt{\frac{1}{a} + \frac{1}{b} + \frac{1}{c} + \frac{1}{d}}
.. versionadded:: 0.4.0
"""
def __init__(
self,
alphabet=None,
tokenizer=None,
intersection_type='crisp',
**kwargs
):
"""Initialize UnigramSubtuple instance.
Parameters
----------
alphabet : Counter, collection, int, or None
This represents the alphabet of possible tokens.
See :ref:`alphabet <alphabet>` description in
:py:class:`_TokenDistance` for details.
tokenizer : _Tokenizer
A tokenizer instance from the :py:mod:`abydos.tokenizer` package
intersection_type : str
Specifies the intersection type, and set type as a result:
See :ref:`intersection_type <intersection_type>` description in
:py:class:`_TokenDistance` for details.
**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.
metric : _Distance
A string distance measure class for use in the ``soft`` and
``fuzzy`` variants.
threshold : float
A threshold value, similarities above which are counted as
members of the intersection for the ``fuzzy`` variant.
.. versionadded:: 0.4.0
"""
super(UnigramSubtuple, self).__init__(
alphabet=alphabet,
tokenizer=tokenizer,
intersection_type=intersection_type,
**kwargs
)
[docs] def sim_score(self, src, tar):
"""Return the unigram subtuple similarity 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
Unigram subtuple similarity
Examples
--------
>>> cmp = UnigramSubtuple()
>>> cmp.sim_score('cat', 'hat')
1.9324426894059226
>>> cmp.sim_score('Niall', 'Neil')
1.4347242883606355
>>> cmp.sim_score('aluminum', 'Catalan')
-1.0866724701675263
>>> cmp.sim_score('ATCG', 'TAGC')
-0.461880260111438
.. versionadded:: 0.4.0
"""
self._tokenize(src, tar)
a = max(1, self._intersection_card())
b = max(1, self._src_only_card())
c = max(1, self._tar_only_card())
d = max(1, self._total_complement_card())
return (
log(a * d / (b * c))
- 3.29 * (1 / a + 1 / b + 1 / c + 1 / d) ** 0.5
)
[docs] def sim(self, src, tar):
"""Return the unigram subtuple similarity 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
Unigram subtuple similarity
Examples
--------
>>> cmp = UnigramSubtuple()
>>> cmp.sim('cat', 'hat')
0.6215275850074894
>>> cmp.sim('Niall', 'Neil')
0.39805896767519555
>>> cmp.sim('aluminum', 'Catalan')
0.0
>>> cmp.sim('ATCG', 'TAGC')
0.0
.. versionadded:: 0.4.0
"""
score = self.sim_score(src, tar)
if score < 0:
return 0.0
return score / max(self.sim_score(src, src), self.sim_score(tar, tar))
if __name__ == '__main__':
import doctest
doctest.testmod()