Elo

This is a library which implements a simple Elo rating system in F#.

Installing & Using

Install from NuGet via Visual Studio's package manager console

PM> install-package Elo

... or using the dotnet command:

$ dotnet add package Elo

Example

Below is an F# example showing how you can use the library. In short - import the Elo namespace, initialise an EloSystem (specifying the starting points, and the K value) then add results to the system. The results are simply the first six games of the 2017 Confederations Cup.

open Elo;

let rankings = EloSystem(EloSettings(32.0, 1000.0))

let round1 = seq {
    yield Result("Russia", "New Zealand", BasicResult.Win)   // Russia beat New Zealand
    yield Result("Portugal", "Mexico", BasicResult.Draw)     // Brazil and Afghanistan draw
    yield Result("Cameroon", "Chile", BasicResult.Loss)      // Cameron lose to Chile
    yield Result("Australia", "Germany", BasicResult.Loss)   // Australia lose to Germany
    yield Result("Russia", "Portugal", BasicResult.Loss)     // Russia lose to Portgual
    yield Result("Mexico", "New Zealand", BasicResult.Win) } // Mexico beat New Zealand

rankings.AddResults(round1)

for team in rankings.Rankings do printfn "%A" team

This will output the below:

Portugal: 1016
Mexico: 1016
Chile: 1016
Germany: 1016
Russia: 1000
Cameroon: 984
Australia: 984
New Zealand: 968

Results

The result is defined from the perspective of the first team or player, and is simply a float in the range [0.0, 1.0] with 1.0 a win and 0.0 is a loss. There are currently two different scoring systems defined - BasicResult and BestOfFive

BasicResult

Enum	Value
BasicResult.Win	1.0
BasicResult.Draw	0.5
BasicResult.Loss	0.0

BestOfFive

Enum	Value
BestOfFive.Score3_0	1.0
BestOfFive.Score3_1	0.8
BestOfFive.Score3_2	0.6
BestOfFive.Score2_3	0.4
BestOfFive.Score1_3	0.2
BestOfFive.Score0_3	0.0