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New Elo Ranking System for Tennis Ladders

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4 years 8 months ago #246 by Trevor Meier
We have created a new rating system for the ladders called the Elo Rating system. This system will replace the True Rank system.

You will still be able to continue using the True Rank system if you are using it now, but all future ladders will not be able to use it.

The Elo Rating system starts each team with a default rating of 1500 points, which will increase as they win and decrease as they lose. The amount of points gained or lost from a game is dependent on the points of the opponent played. For example, if a 2000 point team beats a 1000 point team, very little change will occur to either team's rating. However, if a 2000 point team loses to a 1000 point team, both team's points will change drastically. Teams points will also change more drastically during the first matches that are recorded. This allows teams to reach a stable equilibrium quickly.

The Elo Rating system should be a little more accurate then the True Rank system, and more importantly, easier to understand. If you want to learn more about the math involved, go here:

elorankings.com/

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4 years 8 months ago - 4 years 8 months ago #248 by - Aykol -
Hi Trevor,
This new feature is great. I have a few questions though.

1. I wrote a program that uses Canada's Rogers ELO Rating but using my own table for gains/loss and we also started with initial rating of 1600, 1550 and 1500 for our Level 3.0, 2,5 and 2.0 level players and I've entered all our tournament and ladder matches from last year so we have an up to date ratings. Is it possible to manually enter them in Ladder?

2. Can we use this rating system instead of the Registered Level in tournaments? If not, maybe you can incorporate this in future site upgrade where the player has the option to enter a rating (1500, 1550, etc) aside from the Player Level?

Thanks.
Last edit: 4 years 8 months ago by - Aykol -.

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4 years 8 months ago #249 by - Aykol -
I'll wait for the day when we can use this as the official ranking system instead of the Player Level. I'm assuming that for this to happen. we'll have to change the registered player level from the current 2.0, 2.5, 3.0 etc to ratings 1500, 1450, 1400 and so on.

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4 years 8 months ago #250 by Trevor Meier
The calculated playing levels use a very similar formula based on the same Elo system.

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4 years 8 months ago #251 by Trevor Meier
You can always change a team's points on your tennis ladders. So if you wanted all your 2.5 players to start the ladder at 1450 points, you could do that.

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4 years 8 months ago - 4 years 8 months ago #252 by - Aykol -
Thanks for the prompt reply. Trying to satisfy my curiosity, I applied the ELO on our last year's Ladder and recalculated all players ratings. Here's one match that I want to clarify.

Dennis Aldon 6 10 10 1484 1496 - gained 12
Ray Armada 4 18 18 765 759 - lost 6

Based on the above numbers, the Rogers ELO calculations would have
Dennis gain 6 if he wins, Ray loses 6 points.
Ray gains 12 points if he wins, Dennis loses 12 points.

Since Dennis is the higher rated player, his lost points should be greater than his won points.

And depending on the gain/lost points table, that BIG rating points difference may have earned Dennis ZERO points if he wins and Ray ZERO point lost.
Last edit: 4 years 8 months ago by - Aykol -.

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4 years 8 months ago #253 by - Aykol -

Trevor Meier wrote: You can always change a team's points on your tennis ladders. So if you wanted all your 2.5 players to start the ladder at 1450 points, you could do that.


I was able to change the points but it didn't recalculate with the already played match. It assigned it as the new ladder points.

Before the change:
Carlos Buencamino 8 1 1 1500 1516
Nandi Nacu 0 1 3 1500 1484

After the change
Nandi Nacu Points Change Tooltip 3 4 1484 1400

4 Nandi Nacu Wins: 0
1400 Level: 2.00 Losses: 1

Or will it recalculate it tonight?

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4 years 8 months ago - 4 years 8 months ago #254 by Trevor Meier
You would have to do it manually at the beginning of the ladder so a player would start the ladder at the points corresponding to their playing level.

So, if a 2.5 level player joins your ladder, you can update his points immediately to 1450 (your choice).

There is no calculations at night on the ladders. That is only your calculated playing level as seen on your profile page on right beneath the player's name in small font. This calculated playing level has zero affect on the ladder.
Last edit: 4 years 8 months ago by Trevor Meier.

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4 years 8 months ago #255 by - Aykol -

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4 years 8 months ago #256 by Ted Seymour
Hi Trevor,

I'm glad you have been working on an improved ranking system. Something seems a bit amiss however, at least in the early going. I converted our completed ladder ( www.globaltennisnetwork.com/network/tenn...dder-end-jan-31-2016 ) to the new ELO system and noticed the following for our first three matches:

Match 3
Daniel / Ted 6 1920 / 1080 2120 / 1280
Deb / Rob 2 1920 / 1080 1720 / 880

Match 2
Daniel / Deb 6 1484 / 1484 1920 / 1920
Rob / Ted 4 1516 / 1516 1080 / 1080

Match 1
Rob / Ted 6 1500 / 1500 1516 / 1516
Daniel / Deb 0 1500 / 1500 1484 / 1484

What you'll see is:
- that there was very little points movement (16 points) after the first match - fine
- the second match (which is a repeat of the first match) has a monstrous swing in points (436 points). Why?
- So after the 2nd match, even though everybody was 1-1, there was now a significant differential in points between the players (seems very strange and doesn't reflect reality very much). In addition, the team that lost by a closer score (6-4) now has lower points than the team that got skunked (6-0). Seems unfair.
- We switched up teams for the third match and you'll note that Ted, even though his record is 2-1, has significantly fewer points (440) than Deb, even though Deb is 1-2. Deb, who shares the same 1-2 record as Robert has 840 points more than Rob.

thanks for all your work on this site. I so appreciate it.
ted

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