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
------------------------------------------------------------------------
d.i.barr's Profile: http://www.excelforum.com/member.php...o&userid=15521
View this thread: http://www.excelforum.com/showthread...hreadid=518685

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" wrote in
message ...

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
------------------------------------------------------------------------
d.i.barr's Profile:
http://www.excelforum.com/member.php...o&userid=15521
View this thread: http://www.excelforum.com/showthread...hreadid=518685

Thanks for your help Niek

--
d.i.bar
-----------------------------------------------------------------------
d.i.barr's Profile: http://www.excelforum.com/member.php...fo&userid=1552
View this thread: http://www.excelforum.com/showthread.php?threadid=51868