abydos.distance.compression.dist_ncd_arith() - Code Metrics - Inspection of "Merge pull request #127 from chrislit/fix_builds" - chrislit/abydos - Measure and Improve Code Quality continuously with Scrutinizer

Completed

Branch — master (87ccc1)

by Chris

created 2018-10-23 03:59 UTC

abydos.distance.compression.dist_ncd_arith() A

↳ Parent: abydos.distance.compression

Complexity

Conditions

Size

Total Lines	34
Code Lines	11

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
cc	3
eloc	11
nop	3
dl	0
loc	34
rs	9.85
c	0
b	0
f	0

# -*- coding: utf-8 -*-

# Copyright 2014-2018 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.compression.

The distance.compression module implements compression distance measures.
"""

from __future__ import division, unicode_literals

from codecs import encode
from sys import modules

from ..compression import arithmetic, rle

try:
    import lzma
except ImportError:  # pragma: no cover
    # If the system lacks the lzma library, that's fine, but lzma compression
    # similarity won't be supported.
    lzma = None

__all__ = ['dist_ncd_arith', 'dist_ncd_bwtrle', 'dist_ncd_bz2',
           'dist_ncd_lzma', 'dist_ncd_rle', 'dist_ncd_zlib', 'sim_ncd_arith',
           'sim_ncd_bwtrle', 'sim_ncd_bz2', 'sim_ncd_lzma', 'sim_ncd_rle',
           'sim_ncd_zlib']


def dist_ncd_arith(src, tar, probs=None):
    """Return the NCD between two strings using arithmetic coding.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :param dict probs: a dictionary trained with arithmetic.train (for the
        arith compressor only)
    :returns: compression distance
    :rtype: float

    >>> dist_ncd_arith('cat', 'hat')
    0.5454545454545454
    >>> dist_ncd_arith('Niall', 'Neil')
    0.6875
    >>> dist_ncd_arith('aluminum', 'Catalan')
    0.8275862068965517
    >>> dist_ncd_arith('ATCG', 'TAGC')
    0.6923076923076923
    """
    if src == tar:
        return 0.0

    if probs is None:
        # lacking a reasonable dictionary, train on the strings themselves
        probs = arithmetic.train(src + tar)
    src_comp = arithmetic.encode(src, probs)[1]
    tar_comp = arithmetic.encode(tar, probs)[1]
    concat_comp = arithmetic.encode(src + tar, probs)[1]
    concat_comp2 = arithmetic.encode(tar + src, probs)[1]

    return ((min(concat_comp, concat_comp2) - min(src_comp, tar_comp)) /
            max(src_comp, tar_comp))


def sim_ncd_arith(src, tar, probs=None):
    """Return the NCD similarity between two strings using arithmetic coding.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :param dict probs: a dictionary trained with arithmetic.train (for the
        arith compressor only)
    :returns: compression similarity
    :rtype: float

    >>> sim_ncd_arith('cat', 'hat')
    0.4545454545454546
    >>> sim_ncd_arith('Niall', 'Neil')
    0.3125
    >>> sim_ncd_arith('aluminum', 'Catalan')
    0.1724137931034483
    >>> sim_ncd_arith('ATCG', 'TAGC')
    0.3076923076923077
    """
    return 1-dist_ncd_arith(src, tar, probs)


def dist_ncd_rle(src, tar, use_bwt=False):
    """Return the NCD between two strings using RLE.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :param bool use_bwt: boolean indicating whether to perform BWT encoding
        before RLE encoding
    :returns: compression distance
    :rtype: float

    >>> dist_ncd_rle('cat', 'hat')
    1.0
    >>> dist_ncd_rle('Niall', 'Neil')
    1.0
    >>> dist_ncd_rle('aluminum', 'Catalan')
    1.0
    >>> dist_ncd_rle('ATCG', 'TAGC')
    1.0
    """
    if src == tar:
        return 0.0

    src_comp = rle.encode(src, use_bwt)
    tar_comp = rle.encode(tar, use_bwt)
    concat_comp = rle.encode(src + tar, use_bwt)
    concat_comp2 = rle.encode(tar + src, use_bwt)

    return ((min(len(concat_comp), len(concat_comp2)) -
             min(len(src_comp), len(tar_comp))) /
            max(len(src_comp), len(tar_comp)))


def sim_ncd_rle(src, tar, use_bwt=False):
    """Return the NCD similarity between two strings using RLE.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :param bool use_bwt: boolean indicating whether to perform BWT encoding
        before RLE encoding
    :returns: compression similarity
    :rtype: float

    >>> sim_ncd_rle('cat', 'hat')
    0.0
    >>> sim_ncd_rle('Niall', 'Neil')
    0.0
    >>> sim_ncd_rle('aluminum', 'Catalan')
    0.0
    >>> sim_ncd_rle('ATCG', 'TAGC')
    0.0
    """
    return 1 - dist_ncd_rle(src, tar, use_bwt)


def dist_ncd_bwtrle(src, tar):
    """Return the NCD between two strings using BWT plus RLE.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :returns: compression distance
    :rtype: float

    >>> dist_ncd_bwtrle('cat', 'hat')
    0.75
    >>> dist_ncd_bwtrle('Niall', 'Neil')
    0.8333333333333334
    >>> dist_ncd_bwtrle('aluminum', 'Catalan')
    1.0
    >>> dist_ncd_bwtrle('ATCG', 'TAGC')
    0.8
    """
    return dist_ncd_rle(src, tar, True)


def sim_ncd_bwtrle(src, tar):
    """Return the NCD similarity between two strings using BWT plus RLE.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :returns: compression similarity
    :rtype: float

    >>> sim_ncd_bwtrle('cat', 'hat')
    0.25
    >>> sim_ncd_bwtrle('Niall', 'Neil')
    0.16666666666666663
    >>> sim_ncd_bwtrle('aluminum', 'Catalan')
    0.0
    >>> sim_ncd_bwtrle('ATCG', 'TAGC')
    0.19999999999999996
    """
    return 1 - dist_ncd_bwtrle(src, tar)


def dist_ncd_zlib(src, tar):

    """Return the NCD between two strings using zlib compression.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :returns: compression distance
    :rtype: float

    >>> dist_ncd_zlib('cat', 'hat')
    0.3333333333333333
    >>> dist_ncd_zlib('Niall', 'Neil')
    0.45454545454545453
    >>> dist_ncd_zlib('aluminum', 'Catalan')
    0.5714285714285714
    >>> dist_ncd_zlib('ATCG', 'TAGC')
    0.4
    """
    if src == tar:
        return 0.0

    src = src.encode('utf-8')
    tar = tar.encode('utf-8')

    src_comp = encode(src, 'zlib_codec')[2:]
    tar_comp = encode(tar, 'zlib_codec')[2:]
    concat_comp = encode(src + tar, 'zlib_codec')[2:]
    concat_comp2 = encode(tar + src, 'zlib_codec')[2:]

    return ((min(len(concat_comp), len(concat_comp2)) -
             min(len(src_comp), len(tar_comp))) /
            max(len(src_comp), len(tar_comp)))


def sim_ncd_zlib(src, tar):
    """Return the NCD similarity between two strings using zlib compression.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :returns: compression similarity
    :rtype: float

    >>> sim_ncd_zlib('cat', 'hat')
    0.6666666666666667
    >>> sim_ncd_zlib('Niall', 'Neil')
    0.5454545454545454
    >>> sim_ncd_zlib('aluminum', 'Catalan')
    0.4285714285714286
    >>> sim_ncd_zlib('ATCG', 'TAGC')
    0.6
    """
    return 1 - dist_ncd_zlib(src, tar)


def dist_ncd_bz2(src, tar):

    """Return the NCD between two strings using bz2 compression.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :returns: compression distance
    :rtype: float

    >>> dist_ncd_bz2('cat', 'hat')
    0.08
    >>> dist_ncd_bz2('Niall', 'Neil')
    0.037037037037037035
    >>> dist_ncd_bz2('aluminum', 'Catalan')
    0.20689655172413793
    >>> dist_ncd_bz2('ATCG', 'TAGC')
    0.037037037037037035
    """
    if src == tar:
        return 0.0

    src = src.encode('utf-8')
    tar = tar.encode('utf-8')

    src_comp = encode(src, 'bz2_codec')[15:]
    tar_comp = encode(tar, 'bz2_codec')[15:]
    concat_comp = encode(src + tar, 'bz2_codec')[15:]
    concat_comp2 = encode(tar + src, 'bz2_codec')[15:]

    return ((min(len(concat_comp), len(concat_comp2)) -
             min(len(src_comp), len(tar_comp))) /
            max(len(src_comp), len(tar_comp)))


def sim_ncd_bz2(src, tar):
    """Return the NCD similarity between two strings using bz2 compression.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :returns: compression similarity
    :rtype: float

    >>> sim_ncd_bz2('cat', 'hat')
    0.92
    >>> sim_ncd_bz2('Niall', 'Neil')
    0.962962962962963
    >>> sim_ncd_bz2('aluminum', 'Catalan')
    0.7931034482758621
    >>> sim_ncd_bz2('ATCG', 'TAGC')
    0.962962962962963
    """
    return 1 - dist_ncd_bz2(src, tar)


def dist_ncd_lzma(src, tar):
    """Return the NCD between two strings using lzma compression.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :returns: compression distance
    :rtype: float

    >>> dist_ncd_lzma('cat', 'hat')
    0.08695652173913043
    >>> dist_ncd_lzma('Niall', 'Neil')
    0.16
    >>> dist_ncd_lzma('aluminum', 'Catalan')
    0.16
    >>> dist_ncd_lzma('ATCG', 'TAGC')
    0.08695652173913043
    """
    if src == tar:
        return 0.0

    src = src.encode('utf-8')
    tar = tar.encode('utf-8')

    if 'lzma' in modules:
        src_comp = lzma.compress(src)[14:]
        tar_comp = lzma.compress(tar)[14:]
        concat_comp = lzma.compress(src + tar)[14:]
        concat_comp2 = lzma.compress(tar + src)[14:]
    else:
        raise ValueError('Install the PylibLZMA module in order to use lzma ' +
                         'compression similarity')

    return ((min(len(concat_comp), len(concat_comp2)) -
             min(len(src_comp), len(tar_comp))) /
            max(len(src_comp), len(tar_comp)))


def sim_ncd_lzma(src, tar):
    """Return the NCD similarity between two strings using lzma compression.

    Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :returns: compression similarity
    :rtype: float

    >>> sim_ncd_lzma('cat', 'hat')
    0.9130434782608696
    >>> sim_ncd_lzma('Niall', 'Neil')
    0.84
    >>> sim_ncd_lzma('aluminum', 'Catalan')
    0.84
    >>> sim_ncd_lzma('ATCG', 'TAGC')
    0.9130434782608696
    """
    return 1 - dist_ncd_lzma(src, tar)


if __name__ == '__main__':
    import doctest
    doctest.testmod()


1		# -- coding: utf-8 --
2
3		# Copyright 2014-2018 by Christopher C. Little.
4		# This file is part of Abydos.
5		#
6		# Abydos is free software: you can redistribute it and/or modify
7		# it under the terms of the GNU General Public License as published by
8		# the Free Software Foundation, either version 3 of the License, or
9		# (at your option) any later version.
10		#
11		# Abydos is distributed in the hope that it will be useful,
12		# but WITHOUT ANY WARRANTY; without even the implied warranty of
13		# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14		# GNU General Public License for more details.
15		#
16		# You should have received a copy of the GNU General Public License
17		# along with Abydos. If not, see <http://www.gnu.org/licenses/>.
18
19		"""abydos.distance.compression.
20
21		The distance.compression module implements compression distance measures.
22		"""
23
24		from __future__ import division, unicode_literals
25
26		from codecs import encode
27		from sys import modules
28
29		from ..compression import arithmetic, rle
30
31		try:
32		import lzma
33		except ImportError: # pragma: no cover
34		# If the system lacks the lzma library, that's fine, but lzma compression
35		# similarity won't be supported.
36		lzma = None
37
38		__all__ = ['dist_ncd_arith', 'dist_ncd_bwtrle', 'dist_ncd_bz2',
39		'dist_ncd_lzma', 'dist_ncd_rle', 'dist_ncd_zlib', 'sim_ncd_arith',
40		'sim_ncd_bwtrle', 'sim_ncd_bz2', 'sim_ncd_lzma', 'sim_ncd_rle',
41		'sim_ncd_zlib']
42
43
44		def dist_ncd_arith(src, tar, probs=None):
45		"""Return the NCD between two strings using arithmetic coding.
46
47		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
48
49		:param str src: source string for comparison
50		:param str tar: target string for comparison
51		:param dict probs: a dictionary trained with arithmetic.train (for the
52		arith compressor only)
53		:returns: compression distance
54		:rtype: float
55
56		>>> dist_ncd_arith('cat', 'hat')
57		0.5454545454545454
58		>>> dist_ncd_arith('Niall', 'Neil')
59		0.6875
60		>>> dist_ncd_arith('aluminum', 'Catalan')
61		0.8275862068965517
62		>>> dist_ncd_arith('ATCG', 'TAGC')
63		0.6923076923076923
64		"""
65		if src == tar:
66		return 0.0
67
68		if probs is None:
69		# lacking a reasonable dictionary, train on the strings themselves
70		probs = arithmetic.train(src + tar)
71		src_comp = arithmetic.encode(src, probs)[1]
72		tar_comp = arithmetic.encode(tar, probs)[1]
73		concat_comp = arithmetic.encode(src + tar, probs)[1]
74		concat_comp2 = arithmetic.encode(tar + src, probs)[1]
75
76		return ((min(concat_comp, concat_comp2) - min(src_comp, tar_comp)) /
77		max(src_comp, tar_comp))
78
79
80		def sim_ncd_arith(src, tar, probs=None):
81		"""Return the NCD similarity between two strings using arithmetic coding.
82
83		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
84
85		:param str src: source string for comparison
86		:param str tar: target string for comparison
87		:param dict probs: a dictionary trained with arithmetic.train (for the
88		arith compressor only)
89		:returns: compression similarity
90		:rtype: float
91
92		>>> sim_ncd_arith('cat', 'hat')
93		0.4545454545454546
94		>>> sim_ncd_arith('Niall', 'Neil')
95		0.3125
96		>>> sim_ncd_arith('aluminum', 'Catalan')
97		0.1724137931034483
98		>>> sim_ncd_arith('ATCG', 'TAGC')
99		0.3076923076923077
100		"""
101		return 1-dist_ncd_arith(src, tar, probs)
102
103
104		def dist_ncd_rle(src, tar, use_bwt=False):
105		"""Return the NCD between two strings using RLE.
106
107		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
108
109		:param str src: source string for comparison
110		:param str tar: target string for comparison
111		:param bool use_bwt: boolean indicating whether to perform BWT encoding
112		before RLE encoding
113		:returns: compression distance
114		:rtype: float
115
116		>>> dist_ncd_rle('cat', 'hat')
117		1.0
118		>>> dist_ncd_rle('Niall', 'Neil')
119		1.0
120		>>> dist_ncd_rle('aluminum', 'Catalan')
121		1.0
122		>>> dist_ncd_rle('ATCG', 'TAGC')
123		1.0
124		"""
125		if src == tar:
126		return 0.0
127
128		src_comp = rle.encode(src, use_bwt)
129		tar_comp = rle.encode(tar, use_bwt)
130		concat_comp = rle.encode(src + tar, use_bwt)
131		concat_comp2 = rle.encode(tar + src, use_bwt)
132
133		return ((min(len(concat_comp), len(concat_comp2)) -
134		min(len(src_comp), len(tar_comp))) /
135		max(len(src_comp), len(tar_comp)))
136
137
138		def sim_ncd_rle(src, tar, use_bwt=False):
139		"""Return the NCD similarity between two strings using RLE.
140
141		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
142
143		:param str src: source string for comparison
144		:param str tar: target string for comparison
145		:param bool use_bwt: boolean indicating whether to perform BWT encoding
146		before RLE encoding
147		:returns: compression similarity
148		:rtype: float
149
150		>>> sim_ncd_rle('cat', 'hat')
151		0.0
152		>>> sim_ncd_rle('Niall', 'Neil')
153		0.0
154		>>> sim_ncd_rle('aluminum', 'Catalan')
155		0.0
156		>>> sim_ncd_rle('ATCG', 'TAGC')
157		0.0
158		"""
159		return 1 - dist_ncd_rle(src, tar, use_bwt)
160
161
162		def dist_ncd_bwtrle(src, tar):
163		"""Return the NCD between two strings using BWT plus RLE.
164
165		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
166
167		:param str src: source string for comparison
168		:param str tar: target string for comparison
169		:returns: compression distance
170		:rtype: float
171
172		>>> dist_ncd_bwtrle('cat', 'hat')
173		0.75
174		>>> dist_ncd_bwtrle('Niall', 'Neil')
175		0.8333333333333334
176		>>> dist_ncd_bwtrle('aluminum', 'Catalan')
177		1.0
178		>>> dist_ncd_bwtrle('ATCG', 'TAGC')
179		0.8
180		"""
181		return dist_ncd_rle(src, tar, True)
182
183
184		def sim_ncd_bwtrle(src, tar):
185		"""Return the NCD similarity between two strings using BWT plus RLE.
186
187		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
188
189		:param str src: source string for comparison
190		:param str tar: target string for comparison
191		:returns: compression similarity
192		:rtype: float
193
194		>>> sim_ncd_bwtrle('cat', 'hat')
195		0.25
196		>>> sim_ncd_bwtrle('Niall', 'Neil')
197		0.16666666666666663
198		>>> sim_ncd_bwtrle('aluminum', 'Catalan')
199		0.0
200		>>> sim_ncd_bwtrle('ATCG', 'TAGC')
201		0.19999999999999996
202		"""
203		return 1 - dist_ncd_bwtrle(src, tar)
204
205
206	View Code Duplication	def dist_ncd_zlib(src, tar):
		0 ignored issues – show Duplication introduced 2018-10-22 23:53 UTC by Report Bug Copy Issue Report This code seems to be duplicated in your project. Loading history...
207		"""Return the NCD between two strings using zlib compression.
208
209		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
210
211		:param str src: source string for comparison
212		:param str tar: target string for comparison
213		:returns: compression distance
214		:rtype: float
215
216		>>> dist_ncd_zlib('cat', 'hat')
217		0.3333333333333333
218		>>> dist_ncd_zlib('Niall', 'Neil')
219		0.45454545454545453
220		>>> dist_ncd_zlib('aluminum', 'Catalan')
221		0.5714285714285714
222		>>> dist_ncd_zlib('ATCG', 'TAGC')
223		0.4
224		"""
225		if src == tar:
226		return 0.0
227
228		src = src.encode('utf-8')
229		tar = tar.encode('utf-8')
230
231		src_comp = encode(src, 'zlib_codec')[2:]
232		tar_comp = encode(tar, 'zlib_codec')[2:]
233		concat_comp = encode(src + tar, 'zlib_codec')[2:]
234		concat_comp2 = encode(tar + src, 'zlib_codec')[2:]
235
236		return ((min(len(concat_comp), len(concat_comp2)) -
237		min(len(src_comp), len(tar_comp))) /
238		max(len(src_comp), len(tar_comp)))
239
240
241		def sim_ncd_zlib(src, tar):
242		"""Return the NCD similarity between two strings using zlib compression.
243
244		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
245
246		:param str src: source string for comparison
247		:param str tar: target string for comparison
248		:returns: compression similarity
249		:rtype: float
250
251		>>> sim_ncd_zlib('cat', 'hat')
252		0.6666666666666667
253		>>> sim_ncd_zlib('Niall', 'Neil')
254		0.5454545454545454
255		>>> sim_ncd_zlib('aluminum', 'Catalan')
256		0.4285714285714286
257		>>> sim_ncd_zlib('ATCG', 'TAGC')
258		0.6
259		"""
260		return 1 - dist_ncd_zlib(src, tar)
261
262
263	View Code Duplication	def dist_ncd_bz2(src, tar):
		0 ignored issues – show Duplication introduced 2018-10-22 23:53 UTC by Report Bug Copy Issue Report This code seems to be duplicated in your project. Loading history...
264		"""Return the NCD between two strings using bz2 compression.
265
266		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
267
268		:param str src: source string for comparison
269		:param str tar: target string for comparison
270		:returns: compression distance
271		:rtype: float
272
273		>>> dist_ncd_bz2('cat', 'hat')
274		0.08
275		>>> dist_ncd_bz2('Niall', 'Neil')
276		0.037037037037037035
277		>>> dist_ncd_bz2('aluminum', 'Catalan')
278		0.20689655172413793
279		>>> dist_ncd_bz2('ATCG', 'TAGC')
280		0.037037037037037035
281		"""
282		if src == tar:
283		return 0.0
284
285		src = src.encode('utf-8')
286		tar = tar.encode('utf-8')
287
288		src_comp = encode(src, 'bz2_codec')[15:]
289		tar_comp = encode(tar, 'bz2_codec')[15:]
290		concat_comp = encode(src + tar, 'bz2_codec')[15:]
291		concat_comp2 = encode(tar + src, 'bz2_codec')[15:]
292
293		return ((min(len(concat_comp), len(concat_comp2)) -
294		min(len(src_comp), len(tar_comp))) /
295		max(len(src_comp), len(tar_comp)))
296
297
298		def sim_ncd_bz2(src, tar):
299		"""Return the NCD similarity between two strings using bz2 compression.
300
301		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
302
303		:param str src: source string for comparison
304		:param str tar: target string for comparison
305		:returns: compression similarity
306		:rtype: float
307
308		>>> sim_ncd_bz2('cat', 'hat')
309		0.92
310		>>> sim_ncd_bz2('Niall', 'Neil')
311		0.962962962962963
312		>>> sim_ncd_bz2('aluminum', 'Catalan')
313		0.7931034482758621
314		>>> sim_ncd_bz2('ATCG', 'TAGC')
315		0.962962962962963
316		"""
317		return 1 - dist_ncd_bz2(src, tar)
318
319
320		def dist_ncd_lzma(src, tar):
321		"""Return the NCD between two strings using lzma compression.
322
323		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
324
325		:param str src: source string for comparison
326		:param str tar: target string for comparison
327		:returns: compression distance
328		:rtype: float
329
330		>>> dist_ncd_lzma('cat', 'hat')
331		0.08695652173913043
332		>>> dist_ncd_lzma('Niall', 'Neil')
333		0.16
334		>>> dist_ncd_lzma('aluminum', 'Catalan')
335		0.16
336		>>> dist_ncd_lzma('ATCG', 'TAGC')
337		0.08695652173913043
338		"""
339		if src == tar:
340		return 0.0
341
342		src = src.encode('utf-8')
343		tar = tar.encode('utf-8')
344
345		if 'lzma' in modules:
346		src_comp = lzma.compress(src)[14:]
347		tar_comp = lzma.compress(tar)[14:]
348		concat_comp = lzma.compress(src + tar)[14:]
349		concat_comp2 = lzma.compress(tar + src)[14:]
350		else:
351		raise ValueError('Install the PylibLZMA module in order to use lzma ' +
352		'compression similarity')
353
354		return ((min(len(concat_comp), len(concat_comp2)) -
355		min(len(src_comp), len(tar_comp))) /
356		max(len(src_comp), len(tar_comp)))
357
358
359		def sim_ncd_lzma(src, tar):
360		"""Return the NCD similarity between two strings using lzma compression.
361
362		Normalized compression distance (NCD) :cite:`Cilibrasi:2005`.
363
364		:param str src: source string for comparison
365		:param str tar: target string for comparison
366		:returns: compression similarity
367		:rtype: float
368
369		>>> sim_ncd_lzma('cat', 'hat')
370		0.9130434782608696
371		>>> sim_ncd_lzma('Niall', 'Neil')
372		0.84
373		>>> sim_ncd_lzma('aluminum', 'Catalan')
374		0.84
375		>>> sim_ncd_lzma('ATCG', 'TAGC')
376		0.9130434782608696
377		"""
378		return 1 - dist_ncd_lzma(src, tar)
379
380
381		if __name__ == '__main__':
382		import doctest
383		doctest.testmod()
384

chrislit / abydos

Branch — master (87ccc1)

abydos.distance.compression.dist_ncd_arith() A

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