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New Elo Ranking System for Tennis Ladders

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4 years 5 months ago #381 by Ted Seymour
I mentioned this awhile back and in light of reading recent comments, I thought I'd add back in to the discussion. My own observations as well as feedback I've received from some of the players on our ladder is that there is far too much impact on ladder points from winning or losing in the first few matches. Poor performance in the first few matches can place you in a deep hole that can be very difficult to climb out of.

On the flip side, we have a player on our ladder who won his first three matches and even though he has gone 7-12 since then (total record 10-12: calculated level 3.67), his ladder ranking remains higher than another player whose record is 33-16 (calculated level 4.68).

As suggested by another here, Starting ladder points based on a multiplier of calculated level might be a good jumping starting point, and having lower impact from initial matches would be most beneficial. I also agree with the possibility of having margin of victory impacting ladder points, so that 6-0 victories are more impactful than 7-6 margins.

Thanks for all you do here. I know this is a complicated party of the site but it does feel important.

Ted
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4 years 5 months ago - 4 years 5 months ago #386 by Trevor Meier
I have changed the k factor to be a set 32. This is the value that was used with the old True Rank System. This will decrease the point swings, especially at the beginning of the ladder.

If you want bigger swings in points, you can change the k factor from the settings page. Keep in mind, initially the k factor was 800/(total matches) with a minimum of 32.

Also, I may add the ability to start teams at their calculated rating * 100. That could be interesting.
Last edit: 4 years 5 months ago by Trevor Meier.

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4 years 5 months ago #387 by Ted Seymour
Thanks Trevor. I think that helps quite a bit. Now I believe the ladder is more reflective of true ladder performance.

In the settings next to the place where you can set your K factor, you may want to have a link which says "k factor explained" which brings in a pop up which explains and gives guidance to the setting of that variable.

Lastly, if you are considering starting ladder players as a multiple of their calculated level, I was thinking it might be best to use a formula something like this:

Starting Ladder Points = 1500 + (Calculated level - 4.0) x 350. This seems to be a reasonable calculating factor, at least on the ladder I run, between Calculated Level and Ladder Points.

Thank you for the speedy response and fix to this. I love that most everyday, this site is becoming better and better suited to the needs of the greater tennis community.
ted
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4 years 5 months ago #388 by Chris Niu
Hi Trevor,

Could you give some idea on the elo-ranking issue happened in my ladder:

www.globaltennisnetwork.com/network/tenn...-rank-challenge-2016

This morning I found that the points for all players changed a lot... The No.1 player in this ladder got around 2000 points and the 10th got about 700. Now everyone's points become closer to 1500. Would you explain a bit why it happened and how I can change it back? Thanks.

Chris

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4 years 5 months ago - 4 years 5 months ago #389 by Trevor Meier
I have reverted the code that caused the issue. I will need to work on it a little tonight.

Sorry guys. I need to allow the old setting to be the default which means allowing a setting for a k factor with a match count divide factor toggle.

Once that is done, you will be able to set it to the way you need.
Last edit: 4 years 5 months ago by Trevor Meier.
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4 years 5 months ago #390 by Trevor Meier
Ok. We are back in business. You will need to update your settings again.

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4 years 5 months ago - 4 years 5 months ago #391 by Trevor Meier
Ted. To get your desired results, change your k factor to 32 and "No" to divide by matches played.
Last edit: 4 years 5 months ago by Trevor Meier.

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4 years 5 months ago #392 by Ted Seymour
Thanks Trevor, I lowered the settings to a K factor of 80 and allowed dividing by matches played. I like the intention of having greater movement in the beginning, but perhaps not quite so much as used to be with the K factor of 800.

Thanks,
ted

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4 years 5 months ago #393 by Trevor Meier
Hey Ted. That makes sense to me. It helps players climb the ladder if they join late.

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4 years 4 months ago #418 by Michael Zieve
Why do players' ratings change when nobody on the entire ladder has played any matches for the previous several days? By my understanding of Elo ratings, this wouldn't happen -- so I must be missing some aspect of how Elo ratings are implemented here.

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