Calculating expected result

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  • Calculating expected result

    Hey folks,

    The CFC formula for calculating a rating change is Rn = Ro + 32 (S - Sx)

    Does anyone know how they calculate the table that corresponds to Sx?

    The table looks like this at the start:

    0-3 .50 .50
    4-10 .51 .49
    11-17 .52 .48
    18-25 .53 .47
    26-32 .54 .46
    33-39 .55 .45
    40-46 .56 .44

    I'd like to write a little script that can auto-calculate for me (no, I don't want to use the CFC's rating calculator).

  • #2
    Re: Calculating expected result

    I probably should have just googled this first.
    Here's a calculation I found online:


    If Player A has true strength RA and Player B has true strength RB, the exact formula (using the logistic curve) for the expected score of Player A is

    Ea = 1 / (1 + (10^((RB-RA)/400)))

    or put differently:

    1 / (1 + 10 ^ (ratingDiff/400))
    Last edited by Denton Cockburn; Thursday, 21st October, 2010, 11:44 AM.

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    • #3
      Re: Calculating expected result

      If you're interested you can find the FIDE tables here:

      http://www.fide.com/fide/handbook.ht...3&view=article

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      • #4
        Re: Calculating expected result

        Thanks Stuart,

        but what I wanted was to pretty much calculate the table for myself :)

        I wrote my little program, so now I can always just do it myself (if I don't want to look it up online).

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        • #5
          Re: Calculating expected result

          Let's see how my weekend goes, maybe I'll write a useful rating calculator program...

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