abydos.stats.confusion_table.ConfusionTable.f2_score() - Code Metrics - Inspection of "Merge pull request #120 from chrislit/modularize" - chrislit/abydos - Measure and Improve Code Quality continuously with Scrutinizer

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ConfusionTable.f2_score() A

↳ Parent: abydos.stats.confusion_table
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# -*- 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/>.

r"""abydos.stats.confusion_table.

This includes the ConfusionTable object, which includes members capable of
calculating the following data based on a confusion table:

    - population counts
    - precision, recall, specificity, negative predictive value, fall-out,
      false discovery rate, accuracy, balanced accuracy, informedness,
      and markedness
    - various means of the precision & recall, including: arithmetic,
      geometric, harmonic, quadratic, logarithmic, contraharmonic,
      identric (exponential), & Hölder (power/generalized) means
    - :math:`F_{\beta}`-scores, :math:`E`-scores, :math:`G`-measures, along
      with special functions for :math:`F_{1}`, :math:`F_{0.5}`, &
      :math:`F_{2}` scores
    - significance & Matthews correlation coefficient calculation
"""

from __future__ import division, unicode_literals

import math

from .mean import aghmean, agmean, amean, cmean, ghmean, gmean, \
    heronian_mean, hmean, hoelder_mean, imean, lehmer_mean, qmean, \
    seiffert_mean

__all__ = ['ConfusionTable']


class ConfusionTable(object):
    """ConfusionTable object.

    This object is initialized by passing either four integers (or a tuple of
    four integers) representing the squares of a confusion table:
    true positives, true negatives, false positives, and false negatives

    The object possesses methods for the calculation of various statistics
    based on the confusion table.
    """

    _tp, _tn, _fp, _fn = 0, 0, 0, 0

    def __init__(self, tp=0, tn=0, fp=0, fn=0):
        """Initialize ConfusionTable.

        :param int tp: true positives (or a tuple, list, or dict); If a tuple
            or list is supplied, it must include 4 values in the order [tp, tn,
            fp, fn]. If a dict is supplied, it must have 4 keys, namely 'tp',
            'tn', 'fp', & 'fn'.
        :param int tn: true negatives
        :param int fp: false positives
        :param int fn: false negatives

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct == ConfusionTable((120, 60, 20, 30))
        True
        >>> ct == ConfusionTable([120, 60, 20, 30])
        True
        >>> ct == ConfusionTable({'tp': 120, 'tn': 60, 'fp': 20, 'fn': 30})
        True
        """
        if isinstance(tp, (tuple, list)):
            if len(tp) == 4:
                self._tp = tp[0]
                self._tn = tp[1]
                self._fp = tp[2]
                self._fn = tp[3]
            else:
                raise AttributeError('ConfusionTable requires a 4-tuple ' +
                                     'when being created from a tuple.')
        elif isinstance(tp, dict):
            if 'tp' in tp:
                self._tp = tp['tp']
            if 'tn' in tp:
                self._tn = tp['tn']
            if 'fp' in tp:
                self._fp = tp['fp']
            if 'fn' in tp:
                self._fn = tp['fn']
        else:
            self._tp = tp
            self._tn = tn
            self._fp = fp
            self._fn = fn

    def __eq__(self, other):
        """Perform eqality (==) comparison.

        Compares a ConfusionTable to another ConfusionTable or its equivalent
        in the form of a tuple, list, or dict.

        :returns: True if two ConfusionTables are the same object or all four
        of their attributes are equal
        :rtype: bool

        >>> ct1 = ConfusionTable(120, 60, 20, 30)
        >>> ct2 = ConfusionTable(120, 60, 20, 30)
        >>> ct3 = ConfusionTable(60, 30, 10, 15)

        >>> ct1 == ct2
        True
        >>> ct1 == ct3
        False

        >>> ct1 != ct2
        False
        >>> ct1 != ct3
        True
        """
        if isinstance(other, ConfusionTable):
            if id(self) == id(other):
                return True
            if ((self._tp == other.true_pos() and
                 self._tn == other.true_neg() and
                 self._fp == other.false_pos() and
                 self._fn == other.false_neg())):
                return True
        elif isinstance(other, (tuple, list)):
            if ((self._tp == other[0] and self._tn == other[1] and
                 self._fp == other[2] and self._fn == other[3])):
                return True
        elif isinstance(other, dict):
            if ((self._tp == other['tp'] and self._tn == other['tn'] and
                 self._fp == other['fp'] and self._fn == other['fn'])):
                return True
        return False

    def __str__(self):
        """Cast to str.

        :returns: a human-readable version of the confusion table
        :rtype: str

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> str(ct)
        'tp:120, tn:60, fp:20, fn:30'
        """
        return ('tp:' + str(self._tp) + ', tn:' + str(self._tn) + ', fp:' +
                str(self._fp) + ', fn:' + str(self._fn))

    def to_tuple(self):
        """Cast to tuple.

        :returns: the confusion table as a 4-tuple (tp, tn, fp, fn)
        :rtype: tuple

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.to_tuple()
        (120, 60, 20, 30)
        """
        return self._tp, self._tn, self._fp, self._fn

    def to_dict(self):
        """Cast to dict.

        :returns: the confusion table as a dict
        :rtype: dict

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> import pprint
        >>> pprint.pprint(ct.to_dict())
        {'fn': 30, 'fp': 20, 'tn': 60, 'tp': 120}
        """
        return {'tp': self._tp, 'tn': self._tn,
                'fp': self._fp, 'fn': self._fn}

    def true_pos(self):
        """Return true positives.

        :returns: the true positives of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.true_pos()
        120
        """
        return self._tp

    def true_neg(self):
        """Return true negatives.

        :returns: the true negatives of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.true_neg()
        60
        """
        return self._tn

    def false_pos(self):
        """Return false positives.

        :returns: the false positives of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.false_pos()
        20
        """
        return self._fp

    def false_neg(self):
        """Return false negatives.

        :returns: the false negatives of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.false_neg()
        30
        """
        return self._fn

    def correct_pop(self):
        """Return correct population.

        :returns: the correct population of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.correct_pop()
        180
        """
        return self._tp + self._tn

    def error_pop(self):
        """Return error population.

        :returns: The error population of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.error_pop()
        50
        """
        return self._fp + self._fn

    def test_pos_pop(self):
        """Return test positive population.

        :returns: The test positive population of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.test_pos_pop()
        140
        """
        return self._tp + self._fp

    def test_neg_pop(self):
        """Return test negative population.

        :returns: The test negative population of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.test_neg_pop()
        90
        """
        return self._tn + self._fn

    def cond_pos_pop(self):
        """Return condition positive population.

        :returns: The condition positive population of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.cond_pos_pop()
        150
        """
        return self._tp + self._fn

    def cond_neg_pop(self):
        """Return condition negative population.

        :returns: The condition negative population of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.cond_neg_pop()
        80
        """
        return self._fp + self._tn

    def population(self):
        """Return population, N.

        :returns: The population (N) of the confusion table
        :rtype: int

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.population()
        230
        """
        return self._tp + self._tn + self._fp + self._fn

    def precision(self):
        r"""Return precision.

        Precision is defined as :math:`\frac{tp}{tp + fp}`

        AKA positive predictive value (PPV)

        Cf. https://en.wikipedia.org/wiki/Precision_and_recall

        Cf. https://en.wikipedia.org/wiki/Information_retrieval#Precision

        :returns: The precision of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.precision()
        0.8571428571428571
        """
        if self._tp + self._fp == 0:
            return float('NaN')
        return self._tp / (self._tp + self._fp)

    def precision_gain(self):
        r"""Return gain in precision.

        The gain in precision is defined as:
        :math:`G(precision) = \frac{precision}{random~ precision}`

        Cf. https://en.wikipedia.org/wiki/Gain_(information_retrieval)

        :returns: The gain in precision of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.precision_gain()
        1.3142857142857143
        """
        if self.population() == 0:
            return float('NaN')
        random_precision = self.cond_pos_pop()/self.population()
        return self.precision()/random_precision

    def recall(self):
        r"""Return recall.

        Recall is defined as :math:`\frac{tp}{tp + fn}`

        AKA sensitivity

        AKA true positive rate (TPR)

        Cf. https://en.wikipedia.org/wiki/Precision_and_recall

        Cf. https://en.wikipedia.org/wiki/Sensitivity_(test)

        Cf. https://en.wikipedia.org/wiki/Information_retrieval#Recall

        :returns: The recall of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.recall()
        0.8
        """
        if self._tp + self._fn == 0:
            return float('NaN')
        return self._tp / (self._tp + self._fn)

    def specificity(self):
        r"""Return specificity.

        Specificity is defined as :math:`\frac{tn}{tn + fp}`

        AKA true negative rate (TNR)

        Cf. https://en.wikipedia.org/wiki/Specificity_(tests)

        :returns: The specificity of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.specificity()
        0.75
        """
        if self._tn + self._fp == 0:
            return float('NaN')
        return self._tn / (self._tn + self._fp)

    def npv(self):
        r"""Return negative predictive value (NPV).

        NPV is defined as :math:`\frac{tn}{tn + fn}`

        Cf. https://en.wikipedia.org/wiki/Negative_predictive_value

        :returns: The negative predictive value of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.npv()
        0.6666666666666666
        """
        if self._tn + self._fn == 0:
            return float('NaN')
        return self._tn / (self._tn + self._fn)

    def fallout(self):
        r"""Return fall-out.

        Fall-out is defined as :math:`\frac{fp}{fp + tn}`

        AKA false positive rate (FPR)

        Cf. https://en.wikipedia.org/wiki/Information_retrieval#Fall-out

        :returns: The fall-out of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.fallout()
        0.25
        """
        if self._fp + self._tn == 0:
            return float('NaN')
        return self._fp / (self._fp + self._tn)

    def fdr(self):
        r"""Return false discovery rate (FDR).

        False discovery rate is defined as :math:`\frac{fp}{fp + tp}`

        Cf. https://en.wikipedia.org/wiki/False_discovery_rate

        :returns: The false discovery rate of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.fdr()
        0.14285714285714285
        """
        if self._fp + self._tp == 0:
            return float('NaN')
        return self._fp / (self._fp + self._tp)

    def accuracy(self):
        r"""Return accuracy.

        Accuracy is defined as :math:`\frac{tp + tn}{population}`

        Cf. https://en.wikipedia.org/wiki/Accuracy

        :returns: The accuracy of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.accuracy()
        0.782608695652174
        """
        if self.population() == 0:
            return float('NaN')
        return (self._tp + self._tn) / self.population()

    def accuracy_gain(self):
        r"""Return gain in accuracy.

        The gain in accuracy is defined as:
        :math:`G(accuracy) = \frac{accuracy}{random~ accuracy}`

        Cf. https://en.wikipedia.org/wiki/Gain_(information_retrieval)

        :returns: The gain in accuracy of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.accuracy_gain()
        1.4325259515570934
        """
        if self.population() == 0:
            return float('NaN')
        random_accuracy = ((self.cond_pos_pop()/self.population())**2 +
                           (self.cond_neg_pop()/self.population())**2)
        return self.accuracy()/random_accuracy

    def balanced_accuracy(self):
        r"""Return balanced accuracy.

        Balanced accuracy is defined as
        :math:`\frac{sensitivity + specificity}{2}`

        Cf. https://en.wikipedia.org/wiki/Accuracy

        :returns: The balanced accuracy of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.balanced_accuracy()
        0.775
        """
        return 0.5 * (self.recall() + self.specificity())

    def informedness(self):
        """Return informedness.

        Informedness is defined as :math:`sensitivity + specificity - 1`.

        AKA Youden's J statistic

        AKA DeltaP'

        Cf. https://en.wikipedia.org/wiki/Youden%27s_J_statistic

        Cf.
        http://dspace.flinders.edu.au/xmlui/bitstream/handle/2328/27165/Powers%20Evaluation.pdf

        :returns: The informedness of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.informedness()
        0.55
        """
        return self.recall() + self.specificity() - 1

    def markedness(self):
        """Return markedness.

        Markedness is defined as :math:`precision + npv - 1`

        AKA DeltaP

        Cf. https://en.wikipedia.org/wiki/Youden%27s_J_statistic

        Cf.
        http://dspace.flinders.edu.au/xmlui/bitstream/handle/2328/27165/Powers%20Evaluation.pdf

        :returns: The markedness of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.markedness()
        0.5238095238095237
        """
        return self.precision() + self.npv() - 1

    def pr_amean(self):
        r"""Return arithmetic mean of precision & recall.

        The arithmetic mean of precision and recall is defined as:
        :math:`\frac{precision \cdot recall}{2}`

        Cf. https://en.wikipedia.org/wiki/Arithmetic_mean

        :returns: The arithmetic mean of the confusion table's precision &
            recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_amean()
        0.8285714285714285
        """
        return amean((self.precision(), self.recall()))

    def pr_gmean(self):
        r"""Return geometric mean of precision & recall.

        The geometric mean of precision and recall is defined as:
        :math:`\sqrt{precision \cdot recall}`

        Cf. https://en.wikipedia.org/wiki/Geometric_mean

        :returns: The geometric mean of the confusion table's precision &
            recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_gmean()
        0.828078671210825
        """
        return gmean((self.precision(), self.recall()))

    def pr_hmean(self):
        r"""Return harmonic mean of precision & recall.

        The harmonic mean of precision and recall is defined as:
        :math:`\frac{2 \cdot precision \cdot recall}{precision + recall}`

        Cf. https://en.wikipedia.org/wiki/Harmonic_mean

        :returns: The harmonic mean of the confusion table's precision & recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_hmean()
        0.8275862068965516
        """
        return hmean((self.precision(), self.recall()))

    def pr_qmean(self):
        r"""Return quadratic mean of precision & recall.

        The quadratic mean of precision and recall is defined as:
        :math:`\sqrt{\frac{precision^{2} + recall^{2}}{2}}`

        Cf. https://en.wikipedia.org/wiki/Quadratic_mean

        :returns: The quadratic mean of the confusion table's precision &
            recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_qmean()
        0.8290638930598233
        """
        return qmean((self.precision(), self.recall()))

    def pr_cmean(self):
        r"""Return contraharmonic mean of precision & recall.

        The contraharmonic mean is:
        :math:`\frac{precision^{2} + recall^{2}}{precision + recall}`

        Cf. https://en.wikipedia.org/wiki/Contraharmonic_mean

        :returns: The contraharmonic mean of the confusion table's precision &
            recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_cmean()
        0.8295566502463055
        """
        return cmean((self.precision(), self.recall()))

    def pr_lmean(self):
        r"""Return logarithmic mean of precision & recall.

        The logarithmic mean is:
        0 if either precision or recall is 0,
        the precision if they are equal,
        otherwise :math:`\frac{precision - recall}
        {ln(precision) - ln(recall)}`

        Cf. https://en.wikipedia.org/wiki/Logarithmic_mean

        :returns: The logarithmic mean of the confusion table's precision &
            recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_lmean()
        0.8282429171492667
        """
        precision = self.precision()
        recall = self.recall()
        if not precision or not recall:
            return 0.0
        elif precision == recall:
            return precision
        return ((precision - recall) /
                (math.log(precision) - math.log(recall)))

    def pr_imean(self):
        r"""Return identric (exponential) mean of precision & recall.

        The identric mean is:
        precision if precision = recall,
        otherwise :math:`\frac{1}{e} \cdot
        \sqrt[precision - recall]{\frac{precision^{precision}}
        {recall^{recall}}}`

        Cf. https://en.wikipedia.org/wiki/Identric_mean

        :returns: The identric mean of the confusion table's precision & recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_imean()
        0.8284071826325543
        """
        return imean((self.precision(), self.recall()))

    def pr_seiffert_mean(self):
        r"""Return Seiffert's mean of precision & recall.

        Seiffert's mean of precision and recall is:
        :math:`\frac{precision - recall}{4 \cdot arctan
        \sqrt{\frac{precision}{recall}} - \pi}`

        Cf. http://www.helsinki.fi/~hasto/pp/miaPreprint.pdf

        :returns: Seiffer's mean of the confusion table's precision & recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_seiffert_mean()
        0.8284071696048312
        """
        return seiffert_mean((self.precision(), self.recall()))

    def pr_lehmer_mean(self, exp=2.0):
        r"""Return Lehmer mean of precision & recall.

        The Lehmer mean is:
        :math:`\frac{precision^{exp} + recall^{exp}}
        {precision^{exp-1} + recall^{exp-1}}`

        Cf. https://en.wikipedia.org/wiki/Lehmer_mean

        :param float exp: The exponent of the Lehmer mean
        :returns: The Lehmer mean for the given exponent of the confusion
            table's precision & recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_lehmer_mean()
        0.8295566502463055
        """
        return lehmer_mean((self.precision(), self.recall()), exp)

    def pr_heronian_mean(self):
        r"""Return Heronian mean of precision & recall.

        The Heronian mean of precision and recall is defined as:
        :math:`\frac{precision + \sqrt{precision \cdot recall} + recall}{3}`

        Cf. https://en.wikipedia.org/wiki/Heronian_mean

        :returns: The Heronian mean of the confusion table's precision & recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_heronian_mean()
        0.8284071761178939
        """
        return heronian_mean((self.precision(), self.recall()))

    def pr_hoelder_mean(self, exp=2):
        r"""Return Hölder (power/generalized) mean of precision & recall.

        The power mean of precision and recall is defined as:
        :math:`\frac{1}{2} \cdot
        \sqrt[exp]{precision^{exp} + recall^{exp}}`
        for :math:`exp \ne 0`, and the geometric mean for :math:`exp = 0`

        Cf. https://en.wikipedia.org/wiki/Generalized_mean

        :param float exp: The exponent of the Hölder mean
        :returns: The Hölder mean for the given exponent of the confusion
            table's precision & recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_hoelder_mean()
        0.8290638930598233
        """
        return hoelder_mean((self.precision(), self.recall()), exp)

    def pr_agmean(self):
        """Return arithmetic-geometric mean of precision & recall.

        Iterates between arithmetic & geometric means until they converge to
        a single value (rounded to 12 digits)

        Cf. https://en.wikipedia.org/wiki/Arithmetic-geometric_mean

        :returns: The arithmetic-geometric mean of the confusion table's
            precision & recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_agmean()
        0.8283250315702829
        """
        return agmean((self.precision(), self.recall()))

    def pr_ghmean(self):
        """Return geometric-harmonic mean of precision & recall.

        Iterates between geometric & harmonic means until they converge to
        a single value (rounded to 12 digits)

        Cf. https://en.wikipedia.org/wiki/Geometric-harmonic_mean

        :returns: The geometric-harmonic mean of the confusion table's
            precision & recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_ghmean()
        0.8278323841238441
        """
        return ghmean((self.precision(), self.recall()))

    def pr_aghmean(self):
        """Return arithmetic-geometric-harmonic mean of precision & recall.

        Iterates over arithmetic, geometric, & harmonic means until they
        converge to a single value (rounded to 12 digits), following the
        method described by Raïssouli, Leazizi, & Chergui:
        http://www.emis.de/journals/JIPAM/images/014_08_JIPAM/014_08.pdf

        :returns: The arithmetic-geometric-harmonic mean of the confusion
            table's precision & recall
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_aghmean()
        0.8280786712108288
        """
        return aghmean((self.precision(), self.recall()))

    def fbeta_score(self, beta=1.0):
        r"""Return :math:`F_{\beta}` score.

        :math:`F_{\beta}` for a positive real value :math:`\beta` "measures
        the effectiveness of retrieval with respect to a user who
        attaches :math:`\beta` times as much importance to recall as
        precision" (van Rijsbergen 1979)

        :math:`F_{\beta}` score is defined as:
        :math:`(1 + \beta^2) \cdot \frac{precision \cdot recall}
        {((\beta^2 \cdot precision) + recall)}`

        Cf. https://en.wikipedia.org/wiki/F1_score

        :params float beta: The :math:`\beta` parameter in the above formula
        :returns: The :math:`F_{\beta}` of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.fbeta_score()
        0.8275862068965518
        >>> ct.fbeta_score(beta=0.1)
        0.8565371024734982
        """
        if beta <= 0:
            raise AttributeError('Beta must be a positive real value.')
        precision = self.precision()
        recall = self.recall()
        return ((1 + beta**2) *
                precision * recall / ((beta**2 * precision) + recall))

    def f2_score(self):
        """Return :math:`F_{2}`.

        The :math:`F_{2}` score emphasizes recall over precision in comparison
        to the :math:`F_{1}` score

        Cf. https://en.wikipedia.org/wiki/F1_score

        :returns: The :math:`F_{2}` of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.f2_score()
        0.8108108108108109
        """
        return self.fbeta_score(2.0)

    def fhalf_score(self):
        """Return :math:`F_{0.5}` score.

        The :math:`F_{0.5}` score emphasizes precision over recall in
        comparison to the :math:`F_{1}` score

        Cf. https://en.wikipedia.org/wiki/F1_score

        :returns: The :math:`F_{0.5}` score of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.fhalf_score()
        0.8450704225352114
        """
        return self.fbeta_score(0.5)

    def e_score(self, beta=1):
        r"""Return :math:`E`-score.

        This is Van Rijsbergen's effectiveness measure:
        :math:`E=1-F_{\beta}`.

        Cf. https://en.wikipedia.org/wiki/Information_retrieval#F-measure

        :param float beta: The :math:`\beta` parameter in the above formula
        :returns: The :math:`E`-score of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.e_score()
        0.17241379310344818
        """
        return 1-self.fbeta_score(beta)

    def f1_score(self):
        r"""Return :math:`F_{1}` score.

        :math:`F_{1}` score is the harmonic mean of precision and recall:
        :math:`2 \cdot \frac{precision \cdot recall}{precision + recall}`

        Cf. https://en.wikipedia.org/wiki/F1_score

        :returns: The :math:`F_{1}` of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.f1_score()
        0.8275862068965516
        """
        return self.pr_hmean()

    def f_measure(self):
        r"""Return :math:`F`-measure.

        :math:`F`-measure is the harmonic mean of precision and recall:
        :math:`2 \cdot \frac{precision \cdot recall}{precision + recall}`

        Cf. https://en.wikipedia.org/wiki/F1_score

        :returns: The math:`F`-measure of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.f_measure()
        0.8275862068965516
        """
        return self.pr_hmean()

    def g_measure(self):
        r"""Return G-measure.

        :math:`G`-measure is the geometric mean of precision and recall:
        :math:`\sqrt{precision \cdot recall}`

        This is identical to the Fowlkes–Mallows (FM) index for two
        clusters.

        Cf. https://en.wikipedia.org/wiki/F1_score#G-measure

        Cf. https://en.wikipedia.org/wiki/Fowlkes%E2%80%93Mallows_index

        :returns: The :math:`G`-measure of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.g_measure()
        0.828078671210825
        """
        return self.pr_gmean()

    def mcc(self):
        r"""Return Matthews correlation coefficient (MCC).

        The Matthews correlation coefficient is defined as:
        :math:`\frac{(tp \cdot tn) - (fp \cdot fn)}
        {\sqrt{(tp + fp)(tp + fn)(tn + fp)(tn + fn)}}`

        This is equivalent to the geometric mean of informedness and
        markedness, defined above.

        Cf. https://en.wikipedia.org/wiki/Matthews_correlation_coefficient

        :returns: The Matthews correlation coefficient of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.mcc()
        0.5367450401216932
        """
        if (((self._tp + self._fp) * (self._tp + self._fn) *
             (self._tn + self._fp) * (self._tn + self._fn))) == 0:
            return float('NaN')
        return (((self._tp * self._tn) - (self._fp * self._fn)) /
                math.sqrt((self._tp + self._fp) * (self._tp + self._fn) *
                          (self._tn + self._fp) * (self._tn + self._fn)))

    def significance(self):
        r"""Return the significance, :math:`\chi^{2}`.

        Significance is defined as:
        :math:`\chi^{2} =
        \frac{(tp \cdot tn - fp \cdot fn)^{2} (tp + tn + fp + fn)}
        {((tp + fp)(tp + fn)(tn + fp)(tn + fn)}`

        Also: :math:`\chi^{2} = MCC^{2} \cdot n`

        Cf. https://en.wikipedia.org/wiki/Pearson%27s_chi-square_test

        :returns: The significance of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.significance()
        66.26190476190476
        """
        if (((self._tp + self._fp) * (self._tp + self._fn) *
             (self._tn + self._fp) * (self._tn + self._fn))) == 0:
            return float('NaN')
        return (((self._tp * self._tn - self._fp * self._fn)**2 *
                 (self._tp + self._tn + self._fp + self._fn)) /
                ((self._tp + self._fp) * (self._tp + self._fn) *
                 (self._tn + self._fp) * (self._tn + self._fn)))

    def kappa_statistic(self):
        r"""Return κ statistic.

        The κ statistic is defined as:
        :math:`\kappa = \frac{accuracy - random~ accuracy}
        {1 - random~ accuracy}`

        The κ statistic compares the performance of the classifier relative to
        the performance of a random classifier. κ = 0 indicates performance
        identical to random. κ = 1 indicates perfect predictive success.
        κ = -1 indicates perfect predictive failure.

        :returns: The κ statistic of the confusion table
        :rtype: float

        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.kappa_statistic()
        0.5344129554655871
        """
        if self.population() == 0:
            return float('NaN')
        random_accuracy = (((self._tn + self._fp) *
                            (self._tn + self._fn) +
                            (self._fn + self._tp) *
                            (self._fp + self._tp)) /
                           self.population()**2)
        return (self.accuracy()-random_accuracy) / (1-random_accuracy)


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

chrislit / abydos

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ConfusionTable.f2_score() A

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