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Rating system explained

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RFT

Joined: 09 Oct 2003
Posts: 21

Posted: Fri Apr 30, 16:24

Bryzi, the network programmer, just gave me this doc explaing how the system works. we're not going to relese the exact equations, but this should explain a bit of what's going on.

Quote:

Race Driver 2 Rating System - Overview

The rating system in Race Driver 2 is based on a modification of the ELO system used to rank chess players. All players will start with a Driver Rating of 1500. This will fluctuate quite quickly up and down as they begin to complete races, but all players will generally settle on some rating that reflects their consistency and skill.

Generally, these are the original ELO rating classifications:

Over 2600 - Contenders for the World Championship
2400-2599 - International class players
2200-2399 - National championship finalist
2000-2199 - Regional championship finalist (A Grade)
1800-1999 - Club B Grade player
1600-1799 - Club C Grade player
1400-1599 - Club D Grade player
1200-1399 - Club E Grade player
1000-1199 ? Novice

Before a player begins a race, the system predicts his result based on his rating relative to the other players. Let?s assume we have a two-player race:

Name Rating
Bob 1800
Fred 1400

Bob has a higher rating than Fred so is expected to win. After the race finishes, each user Rating is updated based on the result. The equation takes into account the old ratings, if the user was expected to win, the result of the race and then weights the values based on the difference in positions (up to 4).

So if bob wins:

Pos Name Old Rating New Rating Diff
1 Bob 1800 1805 +5
2 Fred 1400 1395 -5

And if bob loses:

Pos Name Old Rating New Rating Diff
1 Bob 1800 1745 -55
2 Fred 1400 1455 +55

So bob stands to lose a lot more than Fred in this race should he lose. This is mainly because of the large difference in rating (400) between the pair.

In a race with more than 2 players the system simply applies the same rules but with every possible permutation. It then uses the sum of all permutations to give a final rating. Suppose we have the following players participating in a race:

Name Rating
Bob 1800
Fred 1400
Jim 1500
Bert 1600
Pete 1700
Alf 2600
Edna 2000
Ernie 2200

Note that Alf is the hot favourite to win. He is odds on against every other player and will therefore lose more points should he not win. Now suppose the players actually finish in the following order, their new ratings after the race are also shown below:

Pos Name Old Rating New Rating Diff
1 Alf 2600 2602 +2
2 Edna 2000 2015 +15
3 Ernie 2200 2195 -5
4 Jim 1500 1532 +32
5 Pete 1700 1705 +5
6 Bert 1600 1599 -1
7 Fred 1400 1398 -2
8 Bob 1800 1755 -45

Notice that Bob loses a large number of points (45) because he came last and lost against 4 players who he should have beaten. Alf, despite coming first, only increases his rating by 2 points because he was expected to beat everyone and his closest rival has 400 less rating points than him. Jim gains 32 points because he finished 4th and beat 3 people with higher ratings than him.

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Rich Tysoe
Motorsport Community Liason
Codemasters.