Source code for abydos.distance._tarantula

# Copyright 2018-2020 by Christopher C. Little.
# This file is part of Abydos.
#
# Abydos is free software: you can redistribute it and/or modify
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"""abydos.distance._tarantula.

Tarantula similarity
"""

from ._token_distance import _TokenDistance

__all__ = ['Tarantula']


[docs]class Tarantula(_TokenDistance): r"""Tarantula similarity. For two sets X and Y and a population N, Tarantula similarity :cite:`Jones:2005` is .. math:: sim_{Tarantula}(X, Y) = \frac{\frac{|X \cap Y|}{|X \cap Y| + |X \setminus Y|}} {\frac{|X \cap Y|}{|X \cap Y| + |X \setminus Y|} + \frac{|Y \setminus X|} {|Y \setminus X| + |(N \setminus X) \setminus Y|}} In :ref:`2x2 confusion table terms <confusion_table>`, where a+b+c+d=n, this is .. math:: sim_{Tarantula} = \frac{\frac{a}{a+b}}{\frac{a}{a+b} + \frac{c}{c+d}} .. versionadded:: 0.4.0 """ def __init__( self, alphabet=None, tokenizer=None, intersection_type='crisp', **kwargs ): """Initialize Tarantula 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(Tarantula, self).__init__( alphabet=alphabet, tokenizer=tokenizer, intersection_type=intersection_type, **kwargs )
[docs] def sim(self, src, tar): """Return the Tarantula 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 Tarantula similarity Examples -------- >>> cmp = Tarantula() >>> cmp.sim('cat', 'hat') 0.9948979591836735 >>> cmp.sim('Niall', 'Neil') 0.98856416772554 >>> cmp.sim('aluminum', 'Catalan') 0.9249106078665077 >>> 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() d = self._total_complement_card() num = a * (c + d) if num: return num / (a * (2 * c + d) + b * c) return 0.0
if __name__ == '__main__': import doctest doctest.testmod()