Calculating ELO Rating (UDF Query)

[d.i.barr]

I'm putting together a UDF that returns an ELO rating for chess players, however I can't seem to get the probablity of winning section working. How would I write the formula (http://upload.wikimedia.org/math/b/2...06d0cb4ef0.png) as a UDF?

If Ra = 1613 and Rb = 1609, the answer returned from the UDF should = 0.506 (example taken from http://en.wikipedia.org/wiki/ELO_rating_system). It might be something I am doing wrong with bracket positioning but I'm sure it's not.

Ea = 1 / (1 + (10 * ((Rb - Ra) / 400)))

This doen't return 0.506 like the example taken from http://en.wikipedia.org/wiki/ELO_rating_system. Can anyone see where I'm going wrong? Or is there a ELO UDF already out there? Thanks in advance.

[Niek Otten]

Function ELO(Ra As Double, Rb As Double) As Double
ELO = 1 / (1 + 10 ^ ((Rb - Ra) / 400))
End Function


--
Kind regards,

Niek Otten

"d.i.barr" <[email protected]> wrote in
message news:[email protected]...
>
> I'm putting together a UDF that returns an ELO rating for chess players,
> however I can't seem to get the probablity of winning section working.
> How would I write the formula
> (http://upload.wikimedia.org/math/b/2...06d0cb4ef0.png)
> as a UDF?
>
> If Ra = 1613 and Rb = 1609, the answer returned from the UDF should =
> 0.506 (example taken from
> http://en.wikipedia.org/wiki/ELO_rating_system). It might be something
> I am doing wrong with bracket positioning but I'm sure it's not.
>
> Ea = 1 / (1 + (10 * ((Rb - Ra) / 400)))
>
> This doen't return 0.506 like the example taken from
> http://en.wikipedia.org/wiki/ELO_rating_system. Can anyone see where
> I'm going wrong? Or is there a ELO UDF already out there? Thanks in
> advance.
>
>
> --
> d.i.barr
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[d.i.barr]

Thanks for your help Niek.

[lulu1]

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