Source code for abydos.distance._ncd_rle

# Copyright 2014-2020 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._ncd_rle.

NCD using RLE
"""

from ._distance import _Distance
from ..compression import RLE

__all__ = ['NCDrle']


[docs] class NCDrle(_Distance): """Normalized Compression Distance using RLE. Cf. https://en.wikipedia.org/wiki/Run-length_encoding Normalized compression distance (NCD) :cite:`Cilibrasi:2005`. .. versionadded:: 0.3.6 """ _rle = RLE()
[docs] def dist(self, src: str, tar: str) -> float: """Return the NCD between two strings using RLE. Parameters ---------- src : str Source string for comparison tar : str Target string for comparison Returns ------- float Compression distance Examples -------- >>> cmp = NCDrle() >>> cmp.dist('cat', 'hat') 1.0 >>> cmp.dist('Niall', 'Neil') 1.0 >>> cmp.dist('aluminum', 'Catalan') 1.0 >>> cmp.dist('ATCG', 'TAGC') 1.0 .. versionadded:: 0.3.5 .. versionchanged:: 0.3.6 Encapsulated in class """ if src == tar: return 0.0 src_comp = self._rle.encode(src) tar_comp = self._rle.encode(tar) concat_comp = self._rle.encode(src + tar) concat_comp2 = self._rle.encode(tar + src) return ( min(len(concat_comp), len(concat_comp2)) - min(len(src_comp), len(tar_comp)) ) / max(len(src_comp), len(tar_comp))
if __name__ == '__main__': import doctest doctest.testmod()