# Source code for abydos.distance._baulieu_vii

# Copyright 2019-2020 by Christopher C. Little.
# This file is part of Abydos.
#
# Abydos is free software: you can redistribute it and/or modify
# 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._baulieu_vii.

Baulieu VII distance
"""

from ._token_distance import _TokenDistance

__all__ = ['BaulieuVII']

[docs]class BaulieuVII(_TokenDistance):
r"""Baulieu VII distance.

For two sets X and Y and a population N, Baulieu VII distance
:cite:Baulieu:1997 is

.. math::

dist_{BaulieuVII}(X, Y) = \frac{|X \setminus Y| + |Y \setminus X|}
{|N| + |X \cap Y| \cdot (|X \cap Y| - 4)^2}

This is Baulieu's 25th dissimilarity coefficient. This coefficient fails
Baulieu's (P4) property, that :math:D(a+1,b,c,d) \leq D(a,b,c,d) = 0
with equality holding iff :math:D(a,b,c,d) = 0.

In :ref:2x2 confusion table terms <confusion_table>, where a+b+c+d=n,
this is

.. math::

dist_{BaulieuVII} = \frac{b+c}{n + a \cdot (a-4)^2}

"""

def __init__(
self,
alphabet=None,
tokenizer=None,
intersection_type='crisp',
**kwargs
):
"""Initialize BaulieuVII 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.

"""
super(BaulieuVII, self).__init__(
alphabet=alphabet,
tokenizer=tokenizer,
intersection_type=intersection_type,
**kwargs
)

[docs]    def dist(self, src, tar):
"""Return the Baulieu VII 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
Baulieu VII distance

Examples
--------
>>> cmp = BaulieuVII()
>>> cmp.dist('cat', 'hat')
0.005050505050505051
>>> cmp.dist('Niall', 'Neil')
0.008838383838383838
>>> cmp.dist('aluminum', 'Catalan')
0.018891687657430732
>>> cmp.dist('ATCG', 'TAGC')
0.012755102040816327

"""
if src == tar:
return 0.0

self._tokenize(src, tar)

a = self._intersection_card()
bpc = self._src_only_card() + self._tar_only_card()
n = self._population_unique_card()

return bpc / (n + a * (a - 4) ** 2)

if __name__ == '__main__':
import doctest

doctest.testmod()