Source code for whalrus.converters_ballot.converter_ballot_to_levels_interval

# -*- coding: utf-8 -*-
"""
Copyright Sylvain Bouveret, Yann Chevaleyre and François Durand
sylvain.bouveret@imag.fr, yann.chevaleyre@dauphine.fr, fradurand@gmail.com

This file is part of Whalrus.

Whalrus 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.

Whalrus 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 Whalrus.  If not, see <http://www.gnu.org/licenses/>.
"""
import numbers
from whalrus.converters_ballot.converter_ballot import ConverterBallot
from whalrus.converters_ballot.converter_ballot_general import ConverterBallotGeneral
from whalrus.ballots.ballot_veto import BallotVeto
from whalrus.ballots.ballot_plurality import BallotPlurality
from whalrus.ballots.ballot_one_name import BallotOneName
from whalrus.ballots.ballot_levels import BallotLevels
from whalrus.ballots.ballot_order import BallotOrder
from whalrus.scales.scale import Scale
from whalrus.scales.scale_interval import ScaleInterval
from whalrus.scales.scale_from_list import ScaleFromList
from whalrus.scales.scale_from_set import ScaleFromSet
from whalrus.scales.scale_range import ScaleRange
from whalrus.scorers.scorer_borda import ScorerBorda
from whalrus.utils.utils import my_division


[docs]class ConverterBallotToLevelsInterval(ConverterBallot): """0 Default converter to a :class:`BallotLevels` using a :class:`ScaleInterval` (interval of real numbers). Parameters ---------- scale : ScaleInterval borda_unordered_give_points : bool When converting a :class:`BallotOrder` that is not a :class:`BallotLevels`, we use Borda scores (normalized to the interval [``scale.low``, ``scale.high``]. This parameter decides whether the unordered candidates of the ballot give points to the ordered candidates. Cf. :class:`ScorerBorda`. Examples -------- Typical usages: >>> converter = ConverterBallotToLevelsInterval() >>> b = BallotLevels({'a': 1, 'b': .5}, candidates={'a', 'b', 'c'}, scale=ScaleInterval(-1, 1)) >>> converter(b).as_dict {'a': 1, 'b': Fraction(3, 4)} >>> b = BallotLevels({'a': 5, 'b': 4}, candidates={'a', 'b', 'c'}, scale=ScaleRange(0, 5)) >>> converter(b).as_dict {'a': 1, 'b': Fraction(4, 5)} >>> b = BallotLevels({'a': 3, 'b': 0}, candidates={'a', 'b', 'c'}, scale=ScaleFromSet({-1, 0, 3})) >>> converter(b).as_dict {'a': 1, 'b': Fraction(1, 4)} >>> b = BallotLevels({'a': 'Excellent', 'b': 'Very Good'}, candidates={'a', 'b', 'c'}, ... scale=ScaleFromList(['Bad', 'Medium', 'Good', 'Very Good', 'Excellent'])) >>> converter(b).as_dict {'a': 1, 'b': Fraction(3, 4)} >>> converter(BallotOneName('a', candidates={'a', 'b', 'c'})).as_dict {'a': 1, 'b': 0, 'c': 0} >>> converter(BallotPlurality('a', candidates={'a', 'b', 'c'})).as_dict {'a': 1, 'b': 0, 'c': 0} >>> converter(BallotVeto('a', candidates={'a', 'b', 'c'})).as_dict {'a': 0, 'b': 1, 'c': 1} >>> converter('a > b > c').as_dict {'a': 1, 'b': Fraction(1, 2), 'c': 0} Options for converting ordered ballots: >>> b = BallotOrder('a > b > c', candidates={'a', 'b', 'c', 'd', 'e'}) >>> ConverterBallotToLevelsInterval(borda_unordered_give_points=False)(b).as_dict {'a': 1, 'b': Fraction(1, 2), 'c': 0} >>> ConverterBallotToLevelsInterval(borda_unordered_give_points=True)(b).as_dict {'a': 1, 'b': Fraction(3, 4), 'c': Fraction(1, 2)} """ def __init__(self, scale: Scale = ScaleInterval(0, 1), borda_unordered_give_points: bool = True): self.scale = scale self.low = scale.low self.high = scale.high self.borda_unordered_give_points = borda_unordered_give_points def __call__(self, x: object, candidates: set=None) -> BallotLevels: x = ConverterBallotGeneral()(x, candidates=None) if isinstance(x, BallotVeto): if x.candidate is None: return BallotLevels(dict(), candidates=x.candidates, scale=self.scale).restrict(candidates=candidates) return BallotLevels({c: self.low if c == x.candidate else self.high for c in x.candidates}, candidates=x.candidates, scale=self.scale).restrict(candidates=candidates) if isinstance(x, BallotOneName): # Including Plurality if x.candidate is None: return BallotLevels(dict(), candidates=x.candidates, scale=self.scale).restrict(candidates=candidates) return BallotLevels({c: self.high if c == x.candidate else self.low for c in x.candidates}, candidates=x.candidates, scale=self.scale).restrict(candidates=candidates) if isinstance(x, BallotLevels): if not x.scale.is_bounded: if all([isinstance(v, numbers.Number) for v in x.values()]): x_min, x_max = min(x.values()), max(x.values()) if x_min >= self.low and x_max <= self.high: return BallotLevels( x.as_dict, candidates=x.candidates, scale=ScaleInterval(low=self.low, high=self.high)).restrict(candidates=candidates) else: x = BallotLevels(x.as_dict, candidates=x.candidates, scale=ScaleInterval(low=min(x.values()), high=max(x.values()))) else: x = BallotLevels(x.as_dict, candidates=x.candidates, scale=ScaleFromSet(set(x.values()))) try: # Interpret as a cardinal ballot return BallotLevels( {c: self.low + my_division((self.high - self.low) * (v - x.scale.low), (x.scale.high - x.scale.low)) for c, v in x.items()}, candidates=x.candidates, scale=self.scale).restrict(candidates=candidates) except (TypeError, AttributeError): x_scale = x.scale if isinstance(x_scale, ScaleFromList): return BallotLevels( {c: self.low + my_division( (self.high - self.low) * x_scale.as_dict[x[c]], (len(x_scale.levels) - 1)) for c, v in x.items()}, candidates=x.candidates, scale=self.scale).restrict(candidates=candidates) if isinstance(x, BallotOrder): borda = ScorerBorda(ballot=x, candidates=x.candidates, unordered_give_points=self.borda_unordered_give_points).scores_ score_max = len(x.candidates) - 1 if self.borda_unordered_give_points else len(x.candidates_in_b) - 1 return BallotLevels( {c: self.low + my_division((self.high - self.low) * borda[c], score_max) for c in x.candidates_in_b}, candidates=x.candidates, scale=self.scale).restrict(candidates=candidates) raise NotImplementedError