Squash Resources and Links
| Squash Ladder Ranking Algorithm |
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June 19th, 2007: There are a handful of members who play frequently and submit their results to the ladder ranking engine. However, because the Elo rating point changes are net-zero (i.e. the winner gains as many points as the loser loses) we find that these players just end up swapping points amongst themselves without any real reward for playing more frequently than other members. So we have decided to add some point inflation to the scheme in order to reward frequent play and reporting of results. Now winners will receive the Elo points times (1+alpha)% while the loser will only lose (1-beta)% where alpha and beta might be something like 0.10. We will play with these numbers (as well as possibly adjusting D and K now that we have more data) to settle on a better ranking. So please be aware that the ladder is going to be a bit unreliable for the next few days as we test the new code on our test site. March 10th, 2007: We have implemented the Elo Rating System and released it to the main site in today's code update. The Elo Rating System is a statistical method for rating players and is used in games where it is impossible for all players to play against each other (or to play against each other a sufficient number of times in order to come up with a clear ranking). The main fixed parameters in the Elo Rating System are D and K. Here D represents the rating of an average player (in our case we are using 100) and is the initial rating of new members on the ladder. K represents the maximum number of points that a player can change depending on their relative strength. Initially we have set this to 10 but this will change with time. We will later implement a higher K for more decisive victories or for more official competitions. In order to update a member's rating we calculate their win expectancy as WE = 1 / ( 10^(-diff/D) + 1 ) where diff is the difference between the players initial elo ratings. Then the match result R is in the set {1,0.5,0} depending on whether it is {won,drawn,lost}. The new Elo rating is updated with K*(R-WE) points. You can test this with the Elo Calculator to experiment with the outcomes depending on various match outcomes.
Follow these links to access the public ladder, or if you are logged in, you can view the detailed ladder which contains more ladder details and a way to contact members directly.
"The ratings are based on results in tournament and match play weighted according to opponents' strength. 'It is a measuring tool, not a device of reward or punishment', Professor Elo once commented. 'It is a means to compare performances, assess relative strength, not a carrot waved before a rabbit, or a piece of candy given to a child for good behavior.'" -The New York Times, 14 November 1992 For more information on the Elo Rating System, see |
ladder-algorithm
Last Updated: 19 Jun 2007 |
