# 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._masi.
MASI similarity
"""
from ._token_distance import _TokenDistance
__all__ = ['MASI']
[docs]class MASI(_TokenDistance):
r"""MASI similarity.
Measuring Agreement on Set-valued Items (MASI) similarity
:cite:`Passonneau:2006` for two sets X and Y is based on Jaccard
similarity:
.. math::
sim_{Jaccard}(X, Y) = \frac{|X \cap Y|}{|X \cup Y|}
This Jaccard similarity is scaled by a value M, which is:
- 1 if :math:`X = Y`
- :math:`\frac{2}{3}` if :math:`X \subset Y` or :math:`Y \subset X`
- :math:`\frac{1}{3}` if :math:`X \cap Y \neq \emptyset`,
:math:`X \setminus Y \neq \emptyset`, and
:math:`Y \setminus X \neq \emptyset`
- 0 if :math:`X \cap Y = \emptyset`
.. versionadded:: 0.4.0
"""
def __init__(self, tokenizer=None, intersection_type='crisp', **kwargs):
"""Initialize MASI instance.
Parameters
----------
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(MASI, self).__init__(
tokenizer=tokenizer, intersection_type=intersection_type, **kwargs
)
[docs] def sim(self, src, tar):
"""Return the MASI similarity of two strings.
Parameters
----------
src : str
Source string for comparison
tar : str
Target string for comparison
Returns
-------
float
MASI similarity
Examples
--------
>>> cmp = MASI()
>>> cmp.sim('cat', 'hat')
0.1111111111111111
>>> cmp.sim('Niall', 'Neil')
0.07407407407407407
>>> cmp.sim('aluminum', 'Catalan')
0.020833333333333332
>>> cmp.sim('ATCG', 'TAGC')
0.0
.. versionadded:: 0.4.0
"""
if src == tar:
return 1.0
self._tokenize(src, tar)
a = self._intersection_card()
b = self._src_only_card()
c = self._tar_only_card()
abc = self._union_card()
jaccard = a / abc
if b == 0 or c == 0:
monotonicity = 2 / 3
elif a != 0:
monotonicity = 1 / 3
else:
monotonicity = 0.0
return jaccard * monotonicity
if __name__ == '__main__':
import doctest
doctest.testmod()