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Thread: ELO Rating system

  1. #1
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    Exclamation ELO Rating system

    I worked on this for a bit with Myth and this is what we have:

    This is mainly Myth's work (obviously) Thanks Myth

    ----------------------
    Squads start off with 1000 rating points.
    When a TWD game has been played, the new rating of the squad will be determined by the following formula:

    New Rating = Old Rating + K(W-P)

    P = Probablitity of winning
    K = Maximum rating change
    W = 1 if the squad has won, W = 0 if the squad has lost


    P = 1 / (1 + 10^(-difference_in_ratings / 400))
    K = 50





    Example:
    wolvencreed (rating 1000) vs Pallies (rating 1400)

    first we'll calculate the probability of winning of wolvencreed over Pallies:
    difference_in_ratings = 1000-1400 = -400

    P = 1 / (1+10^(-(-400) / 400))
    P = 1 / (1+10^1)
    P = 1 / 11
    P = 0.09 = 9% chance of wolvencreed winning over Pallies.
    then ofcourse, the chance of Pallies winning over wolvencreed is 1-0.09 = 0.91 = 91%

    - Scenario: wolvencreed wins!
    so, for wolvencreed: W = 1
    new rating = old rating + K * (W-P)
    new rating = 1000 + 50 * (1-0.09)
    new rating = 1000 + 45.5 = 1046

    for Pallies: W = 0
    new rating = 1400 + 50 * (0-0.91) = 1400 + (-45.5) = 1354.5 = 1355



    -

    K (maximum rating change) is set to 50 in this example. We're considering to lower K when a squad plays more games.

    -



    This system has been blatantly ripped from the starcraft ladder rating system. ( http://www.battle.net/ladder/ladderfaq.shtml )
    Last edited by Mythrandir; 09-23-2002 at 05:29 AM.

  2. #2
    I'd rather be SubSpacing Webbb Llama v1.5's Avatar
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    Thoroughly confusing but it looks good! Damn I want to play some TWD =)
    I'd rather be SubSpacing.

  3. #3
    sheet Dillusion's Avatar
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    what the fuck did you just say, jesus christ
    I dont play this game anymore.

  4. #4
    Pekkle Wix's Avatar
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    WT !#$%!*%*@%*!&#^$%^!#$)

    seeing that wolvencreed only had a 9% chance of winning, and their rating only went up a snitch seems very insignifcant

  5. #5
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    Actually, K=50 is rather high in ELO. Taken together with that it takes 30 games to reach a significant rating I think wolvencreed should be happy with that large an increase.

  6. #6
    Monkey Whore! aphix's Avatar
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    geez, this is taxing on the old brain..

    Ok, after over, myth then bleen explained it, i think i have it.

    Correct me if im wrong ok. .. (and im taking a mid season perspective)

    ======================

    Onix (1280) vs. Cripples (1631)

    Probability's

    1/(1+10^(-(-351)/400))
    1/(1+10^0.88)
    1/9.8
    ______________
    Onix Wins = 11%
    Crips Wins = 89%

    Scenario1 - Cripples Win

    CnR = 1631+50*(1-0.89)
    CnR = 1631+5.5 = 1637

    OnR = 1280+50*(0-0.11)
    OnR = 1280+(-5.5) = 1275

    Onix's new rating = 1275 (move lower)
    Crip's new rating = 1637(move higher)

    Scenario1 - Onix Win

    OnR = 1280+50*(1-0.11)
    OnR = 1280+45.5 = 1325

    CnR = 1631+50*(0-0.89)
    CnR = 1631+(-44.5) = 1587

    Onix's new rating = 1325 (move higher)
    Crips new rating = 1587 (move lower)

    ======================

    Thats probably all wrong

    -aphix

  7. #7
    Monkey Whore! aphix's Avatar
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    What i have seen in the football version, and other ELO systems on other models is where they take the number of games played into account.

    -aphix

  8. #8
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    yes; K might depend on the games played

  9. #9
    Back for some more... Fiction's Avatar
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    Originally posted by Webbb Llama v1.5
    Thoroughly confusing but it looks good! Damn I want to play some TWD =)
    lmao

    same here, i'm not sure of what's happening there with all those numbers... and x's and parenthesis... but i'm sure you guys put a lot of work into and it'll work! And i'm sure i'll get it sooner or later. Lez get TWD goin

  10. #10
    RabbitRapist
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    how about starting with 10 points..

    win = +1
    lose = -1

    why confuse people?

  11. #11
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    how about no?

  12. #12
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    Originally posted by Mythrandir
    how about no?
    Myth 4 sysop
    I'd rather be SubSpacing.

  13. #13
    Shameless Self Promotion pv=nrt's Avatar
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    starting out at 1 is a bad idea, because then you have to go into decimal points to get detailed scores. not that decimals are that hard but it looks cleaner without having 30 squads scores with a period (isn't it a comma in the rest of the world?) after the first number. you can't just do +/- 1 after each win becuase then old squads wanting to exploit the system could face new squads with barely any basers and win easy points. starting at 1000 is fine. though i personally would like to see K=100. just so that there are more points to be won or lost per game.i n a loser sort of way makes it more exciting.
    To all the virgins, Thanks for nothing
    brookus> my grandmother died when she heard people were using numbers in their names in online games.. it was too much for her little heart

  14. #14
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    makes sense (the K=100 part)

  15. #15
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    The math looks fine to me, it's not really complicated people.


    I suppose there is a problem with say a new "vet" squad forming. They'd start at 1000 points, could beat someone with like 1600 points and knock them down close to 50. With the max possible you could lose being 50 it's not really that huge of a problem, it's still a slight problem though.

    It would be nice if it could be done so losing to a newly formed squad wouldn't knock you down quite as much, maybe only half as much, but would still improve them as much as normal if they won. Thus they could get to their "proper" rating quickly without destroying the ratings of sqauds above them on their way up.

    It would also help out the problem of a group of "vets" creating a fake aliased squad pretending to be new and just take down a highly ranked squad a bunch of points.

    So yeah, something like until a squad has played 5-10 games or so they only drop a squad half as much as usual is my idea. I'm sure you can think of a better mathmatical way to do this, but I'm sure you follow my reasoning.

  16. #16
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    yes

    Ok, hearing this, I agree that K (= the maximum rating change) should drop when a squad has played more.

    K starts off with 50
    K drops with 1 (or 2) by every game played, until K is down to 25

  17. #17
    Shameless Self Promotion pv=nrt's Avatar
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    or instead of doing that restrict the range in which you could challenge. say a squad cannot challenge for a rated game outside of 250 pt difference. that way we eliminate the new vet squad from doing any real damage.

    or as its used in the online utopia game. you cannot challenge outside of 20% of your score. this would also restrict who can challenge who, but as the scores get bigger the range of challenging will also increase.

    example.
    team A has 1450 pts
    team B wants to challenge and has 1300 pts
    with a 20% score difference limit
    team b can challange anyone from 1560-1040 pts.
    therefore team B can challenge team A

    this way K can also stay the same. you dont want the scores to stabilize to much with the low K. using the example from aphix with the assumption that cripples is already down to k=25 they can only get 2.75 points if they win.
    To all the virgins, Thanks for nothing
    brookus> my grandmother died when she heard people were using numbers in their names in online games.. it was too much for her little heart

  18. #18
    Monkey Whore! aphix's Avatar
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    sounds a fair idea, it would also encourage squads to schedule more games, to make sure they keep competitive with the better squads. At least within the said 20%.

    Aswell as stop squads, for example Onix/Crips doing a Michael Shumacher, and gaining a phenomenal lead in points.

    It will keep squads tighter together. But is that what we want, where a squad lower down the rankings is unable to try and give say Onix a run for their money in a game of javs.

    Dosn't this partly remove the element of fun.

    Also another thing to consider is that ultimatley it is the squad owners decision to accept or decline the challange, if he/she accepts and they loose, and move down the rankings due to a poor judgement of the competition, the squad will just have to suffer the consequences, making further challanges to claw their way back up the ladder. It also goes for a squad who think they can take on the big boys, and get a good ass whipping, becuase of it.

    A squad isnt successfull only becuase it has good players, but good management too, a captain who knows which battles he can win, and which ones he should walk away from. Untill his squad is stronger/more competitive.

    I think myths suggestion would allow greater competition, and lead to a more exiciting season.

    Although PV's idea does make a hell of allot of sense.. im sitting o nthe wall on this one

    -aphix

  19. #19
    So it goes
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    Wow, lots of subspace guys play Utopia. Great game

  20. #20
    I'd rather be SubSpacing Webbb Llama v1.5's Avatar
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    It just occured to me-

    If a squad starts off badly say- losing 15 of their first 20 games then their K would drop so that it'd be very difficult for them to raise their rating, so they'd just quit or start a new squad?

    Am I misunderstanding it?
    I'd rather be SubSpacing.

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