# 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._unknown_i.
Unknown I similarity
"""
from ._token_distance import _TokenDistance
__all__ = ['UnknownI']
[docs]class UnknownI(_TokenDistance):
r"""Unknown I similarity.
For two sets X and Y, the Unknown I similarity is based on
Mountford similarity :cite:`Mountford:1962` :class:`Mountford`.
.. math::
sim_{UnknownI}(X, Y) =
\frac{2(|X \cap Y|+1)}{2((|X|+2)\cdot(|Y|+2))-
(|X|+|Y|+4)\cdot(|X \cap Y|+1)}
In :ref:`2x2 confusion table terms <confusion_table>`, where a+b+c+d=n,
this is
.. math::
sim_{UnknownI} =
\frac{2(a+1)}{2(a+b+2)(a+c+2)-(2a+b+c+4)(a+1)}
.. versionadded:: 0.4.0
"""
def __init__(self, tokenizer=None, intersection_type='crisp', **kwargs):
"""Initialize UnknownI 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(UnknownI, self).__init__(
tokenizer=tokenizer, intersection_type=intersection_type, **kwargs
)
[docs] def sim(self, src, tar):
"""Return the Unknown I 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
Unknown I similarity
Examples
--------
>>> cmp = UnknownI()
>>> cmp.sim('cat', 'hat')
0.16666666666666666
>>> cmp.sim('Niall', 'Neil')
0.08955223880597014
>>> cmp.sim('aluminum', 'Catalan')
0.02247191011235955
>>> cmp.sim('ATCG', 'TAGC')
0.023809523809523808
.. versionadded:: 0.4.0
"""
self._tokenize(src, tar)
a = self._intersection_card() + 1
b = self._src_only_card() + 1
c = self._tar_only_card() + 1
return 2.0 * a / (c * (a + 2.0 * b) + a * b)
if __name__ == '__main__':
import doctest
doctest.testmod()