NAME

Games::Ratings::Go::EGF - calculate changes to EGF ratings (GoR)

VERSION

This document describes Games::Ratings::Go::EGF version 0.0.1

SYNOPSIS

 use Games::Ratings::Go::EGF;

 my $player = Games::Ratings::Go::EGF->new();
 $player->set_rating(2240);
 $player->add_game( {
                      opponent_rating => 2114,
                      result          => 'win',   ## or 'draw' or 'loss'
                      handicap        => '+5',    ## got 5 handicap
                                                  ## or '-2': gave 2 h.
                                                  ## can be ommitted
                    }
                  );

 my $rating_change = $player->get_rating_change();
 my $new_rating = $player->get_new_rating();

DESCRIPTION

This module provides methods to calculate EGF rating (GoR) changes for one player, having played one or more rated games. Gains and losses are calculated according to the EGF rating rules (cmp. EGF Official ratings: http://gemma.ujf.cas.cz/~cieply/GO/gor.html).

Basically EGF uses a formula to calculate scoring probabilities in dependence from rating differences between players: Se(A) = 1/(e^[D/a] + 1).

Furthermore EGF uses a coefficient ('con') depending on the current rating which reduces rating change for stronger players and increases rating change for weaker players: Rnew - Rold = con * (Sa - Se).

INTERFACE

This modules provides the following methods specific to EGF ratings. Other (more generic) methods for rating calculation are provided by Games::Ratings. Please check the documentation of Games::Ratings for those methods.

get_rating_change

  my $rating_change = $player->get_rating_change();

Calculate rating changes for all stored games and return sum of those changes.

get_new_rating

  my $new_rating = $player->get_new_rating();

Calculate new rating after the given games.

get_points_expected

  my $points_expected = $player->get_points_expected();

Calculate expected points according to rating differences between own rating and opponents ratings.

CONFIGURATION AND ENVIRONMENT

Games::Ratings requires no configuration files or environment variables.

DEPENDENCIES

This module relies on Games::Ratings which provides some generic methods, e.g. * new() * get_rating() * set_rating() * get_coefficient() * set_coefficient() * add_game() * remove_all_games() * DESTROY()

DIAGNOSTICS

At the moment, there are no error or warning messages that the module can generate.

Error message here, perhaps with %s placeholders

[Description of error here]

Another error message here

[Description of error here]

[Et cetera, et cetera]

INCOMPATIBILITIES

None reported.

BUGS AND LIMITATIONS

No bugs have been reported.

At the moment, it's not possible to compute a EGF rating for a previously unrated player.

Please report any bugs or feature requests to bug-games-ratings@rt.cpan.org, or through the web interface at http://rt.cpan.org.

AUTHOR

Christian Bartolomaeus <bartolin@gmx.de>

ACKNOWLEDGMENTS

Many thanks to Ales Cieply for answering my questions about the EGF rating system.

SEE ALSO

http://en.wikipedia.org/wiki/Elo_rating for informations about the Elo system.

http://gemma.ujf.cas.cz/~cieply/GO/gor.html for informations about the EGF rating system.

LICENCE AND COPYRIGHT

Copyright (c) 2008, Christian Bartolomaeus <bartolin@gmx.de>. All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlartistic.

DISCLAIMER OF WARRANTY

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.