+package Games::Ratings::LogisticElo;
+
+use 5.014000;
+use strict;
+use warnings;
+use parent qw/Exporter Games::Ratings/;
+
+our @EXPORT_OK = qw/multi_elo/;
+our @EXPORT = qw//;
+our $VERSION = '0.001';
+
+use List::Util qw/sum/;
+
+sub get_rating_change {
+ my ($self) = @_;
+
+ my $own_rating = $self->get_rating;
+ my $K = $self->get_coefficient;
+
+ my $expected = sum map {
+ my $exp = ($_->{opponent_rating} - $own_rating) / 400;
+ 1 / (1 + 10 ** $exp)
+ } $self->get_all_games;
+
+ my $actual = sum map {
+ Games::Ratings::_get_numerical_result($_->{result})
+ } $self->get_all_games;
+
+ $K * ($actual - $expected)
+}
+
+sub get_new_rating {
+ my ($self) = @_;
+ $self->get_rating + $self->get_rating_change
+}
+
+sub multi_elo {
+ my @args = @_;
+ my $K = ref $args[0] ? 15 : shift @args;
+
+ my @newratings = map {
+ my $player = __PACKAGE__->new;
+ $player->set_rating($_->[0]);
+ $player->set_coefficient($K);
+ for my $opponent (@args) {
+ $player->add_game({
+ opponent_rating => $opponent->[0],
+ result =>
+ $_->[1] > $opponent->[1] ? 'win' :
+ $_->[1] < $opponent->[1] ? 'loss' : 'draw'
+ })
+ }
+ $player->get_new_rating
+ } @args;
+
+ wantarray ? @newratings : \@newratings
+}
+
+1;
+__END__
+
+=encoding utf-8
+
+=head1 NAME
+
+Games::Ratings::LogisticElo - calculate changes to logistic curve Elo ratings
+
+=head1 SYNOPSIS
+
+ use Games::Ratings::LogisticElo;
+ my $player = Games::Ratings::LogisticElo->new;
+ $player->set_rating(2240);
+ $player->set_coefficient(15);
+ $player->add_game({
+ opponent_rating => 2114,
+ result => 'win', ## or 'draw' or 'loss'
+ });
+ say 'Rating change: ' . $player->get_rating_change;
+ say 'New rating: ' . $player->get_new_rating;
+
+ use Games::Ratings::LogisticElo qw/multi_elo/;
+ my @results = [2240, 3], [2114, 2], [2300, 1];
+ my @new_ratings = multi_elo 15, @results;
+ say 'Rating changes for this comp: ', join ', ',
+ map { $new_ratings[$_] - $results[$_]->[0] } 0 .. $#results;
+
+=head1 DESCRIPTION
+
+This module provides methods to calculate Elo rating changes. Unlike
+L<Games::Ratings::Chess::FIDE>, this Elo implementation uses the
+logistic distribution instead of the standard distribution.
+
+This module can be used both for a single player who played multiple
+rated games, and for a single competition with an arbitrary number of
+players.
+
+=head1 FUNCTIONS
+
+Games::Ratings::LogisticElo inherits from L<Games::Ratings>, see that
+module's documentation for information about the inherited methods.
+
+Nothing is exported by default, the function B<multi_elo> can be
+exported on request.
+
+=over
+
+=item B<$self>->I<get_rating_change>
+
+Computes and returns how much a player's rating changes after the
+games added.
+
+=item B<$self>->I<get_new_rating>
+
+Adds the result of I<get_rating_change> to the old rating of the
+player and returns this.
+
+=item B<multi_elo> [$coefficient], @results
+
+Computes the ratings after a competition with an arbitrary number of
+players.
+
+The first argument is the coefficient. It is optional, with the
+default coefficient being 15. The next arguments are the results of
+the players. Each result is a 2-element arrayref, the first element
+being the Elo rating of the player, and the second element being the
+score that player obtained. The scores are only used to compare
+players, their absolute values are irrelevant.
+
+The return value is a list (in list context) or arrayref (in scalar
+context) of ratings of all players after the competition, in the same
+order as the arguments.
+
+This function computes the ratings by considering that each player
+played a game with every other player, with the winner of every game
+being the player who got the highest score.
+
+=back
+
+
+=head1 SEE ALSO
+
+L<Games::Ratings::Chess::FIDE>, L<Games::Ratings>
+
+L<https://en.wikipedia.org/wiki/Elo_rating>
+
+=head1 AUTHOR
+
+Marius Gavrilescu <marius@ieval.ro>
+
+=head1 COPYRIGHT AND LICENSE
+
+Copyright (C) 2016 by Marius Gavrilescu
+
+This library is free software; you can redistribute it and/or modify
+it under the same terms as Perl itself, either Perl version 5.22.2 or,
+at your option, any later version of Perl 5 you may have available.
+
+
+=cut
projects / games-ratings-logisticelo.git / commitdiff