# 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._rouge_l.
Rouge-L similarity
"""
from . import LCSseq
from ._distance import _Distance
__all__ = ['RougeL']
[docs]class RougeL(_Distance):
r"""Rouge-L similarity.
Rouge-L similarity :cite:`Lin:2004`
.. versionadded:: 0.4.0
"""
_lcs = LCSseq()
def __init__(self, **kwargs):
"""Initialize RougeL instance.
Parameters
----------
**kwargs
Arbitrary keyword arguments
.. versionadded:: 0.4.0
"""
super(RougeL, self).__init__(**kwargs)
[docs] def sim(self, src, tar, beta=8):
"""Return the Rouge-L similarity of two strings.
Parameters
----------
src : str
Source string for comparison
tar : str
Target string for comparison
beta : int or float
A weighting factor to prejudice similarity towards src
Returns
-------
float
Rouge-L similarity
Examples
--------
>>> cmp = RougeL()
>>> cmp.sim('cat', 'hat')
0.6666666666666666
>>> cmp.sim('Niall', 'Neil')
0.6018518518518519
>>> cmp.sim('aluminum', 'Catalan')
0.3757225433526012
>>> cmp.sim('ATCG', 'TAGC')
0.5
.. versionadded:: 0.4.0
"""
if src == tar:
return 1.0
if not src or not tar:
return 0.0
lcs_len = len(self._lcs.lcsseq(src, tar))
r_lcs = lcs_len / len(src)
p_lcs = lcs_len / len(tar)
beta_sq = beta * beta
if r_lcs and p_lcs:
return (1 + beta_sq) * r_lcs * p_lcs / (r_lcs + beta_sq * p_lcs)
return 0.0
if __name__ == '__main__':
import doctest
doctest.testmod()