Working With Elo - Topic

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Joined: Feb 19 2012

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Sep 24 2017 06:07pm

Hey.. so I'm working on a small project that I need to build an Elo system into...

So I have a DB and each player has a rating assigned to them.

When inputting results of a match I need to adjust their rating accordingly.

The layout is as follows.

1: GUI Opens
2: SQL Select statement to grab all players names/rating
3: User selects the winner
4: User selects the loser (Cannot be done until a winner is selected)
5: SQL statement is fired to grab winners rating
6: SQL statement is fired to grab losers rating
7: Do Elo calculations
8: Spit out each players adjusted rating.

So I have 1-6 done, just need to figure out how to express their adjusted ratings.

I'm doing this in VB.net but the language doesn't matter since its just arithmetic's and can be used in all languages.

For the purpose of this example assume:

WinningPlayersRating = "1500"
LossingPlayersRating = "1300"

And hopefully once I see this expression I can figure out the following

WinningPlayersRating = "1500"
LossingPlayersRating = "1600"

And

WinningPlayersRating = "1500"
LossingPlayersRating = "1500"

Thanks for the help!

waraholic

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Posts: 1,039

Joined: Jul 8 2008

Gold: 1,939.50

Sep 24 2017 06:13pm

Edit: Stupid me I was thinking of 'elo' as defined by numerous video games that isn't actually 'elo' as defined by this wiki page: https://en.wikipedia.org/wiki/Elo_rating_system
Do you wish to implement that algorithm? Here is some source code that does it in java (you should be able to read it if you are writing VB) https://github.com/radoneman/elo-rating-multiplayer/blob/master/src/com/elo/EloRating.java

This post was edited by waraholic on Sep 24 2017 06:28pm

Damein

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Posts: 4,905

Joined: Feb 19 2012

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Sep 24 2017 07:10pm

Hey, thanks for the input. I went from that to

https://dataskeptic.com/blog/methods/2017/calculating-an-elo-rating

Which broke it down very well for me

Code

Dim Rating1 = 2853
Dim Rating2 = 2400
Dim ExpectedRating1 As Decimal
Dim ExpectedRating2 As Decimal

Dim Calc1 As Decimal
Dim Calc2 As Decimal

Calc1 = 10 ^ (Rating1 / 400)
Calc2 = 10 ^ (Rating2 / 400)

Calc1 = Math.Round(Calc1, 5)
Calc2 = Math.Round(Calc2, 5)

ExpectedRating1 = Calc1 / (Calc1 + Calc2)
ExpectedRating2 = Calc2 / (Calc2 + Calc1)

ExpectedRating1 = Math.Round(ExpectedRating1, 5)
ExpectedRating2 = Math.Round(ExpectedRating2, 5)

Calc1 = Rating1 + 40 * (1 - ExpectedRating1)
Calc1 = Math.Round(Calc1)
Calc2 = Rating2 + 40 * (0 - ExpectedRating2)
Calc2 = Math.Round(Calc2)

Dim Final As String
Dim Final2 As String

Final = Calc1
Final2 = Calc2

MessageBox.Show(Final + vbNewLine + Final2)

So thus

PlayerA's new rating = 2,856
PlayerB's new rating = 2,397

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