Make ELO more stable (show mean over last ~100 games)

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Silene
Posts: 99
Joined: 23 October 2013, 17:50

Make ELO more stable (show mean over last ~100 games)

Post by Silene » 16 May 2019, 10:40

I feel like ELO is going up and down a lot. If I have a winning/losing-streak, ELO is sometimes going up/down by a lot more than 100 points. I think that's not good, because
  1. my skill didn't change that much (if at all) and
  2. my opponents gain more/less ELO by playing against me depending on wether they play me after a good/bad streak - which is not fair to them because my skill (and therefore the difficulty to beat me) is the same for them no matter when they play me
I think it would be good to have an ELO-curve that is more "smooth" around the real value (that represents my real strength)
Compare to how it's done on this site (no board-games but it doesn't matter): https://www.croco-puzzle.com/Raetselspa ... /index.php
--> click any name to show their rank-graph
Black line: shows rating from day-to-day
Green line: shows mean over black line in last 50 days
Red line: shows mean over black line in last 200 days

ELO on BGA right now is very similar to the Black line
But I think it would be great to show the player's level similar to the red line

How to do it
  • Calculate "daily-ELO" as-is (same formula).
  • In Addition calculate "real-ELO" as mean over daily-ELO after the last 100 games (or another amount - maybe depending on number of games played by the player)
  • After a game, compare my "daily-ELO" with my opponents "real-ELO" to calculate my new "daily-ELO"
  • and compare THEIR "daily-ELO" with my "real-ELO" to calculate their new "daily-ELO"
  • for most purposes show "real-ELO" (on profile-page, on game-tables before joining,...). In statistics show both (i.e. on calculation after the game show what you gained in "daily-ELO" - "real-ELO" is not gonna change much anyway (which is good)
Pros:
  • Fair ELO-change to the opponent (depends on real strength and not on a random previous win/loss-streak)
  • Almost impossible to reach an unrealistic maximum point by a lucky random walk.
  • Not much point in settleing on a good ELO because a single game doesn't change that much.
Cons:
  • More complicate for the site (and to implement) and maybe confusing for new players
  • Needs a bunch of games to settle while not yet around real strength. (Maybe it would be good to exclude first ~100 games from real-ELO-calculation or take fewer games into account until you're somewhat settled around a realistic value)

I know there are other threads about ranking and leaderboard. This is about ELO as a measurement of skill - no matter when you played. Please don't write about ranking-list here. I think those should be separated (i.e. RANK could be calculated by ELO modified by recent activity or so but that's not what this thread is about)

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