In addition to the main scoring system, Warlocks get an Elo rank. New warlocks start with a rank of 1500. When you win, your Elo rank goes up. When you lose, it goes down. If you win against someone whose Elo rank is higher than yours, your rank goes up more and their rank goes down more.
Elo ratings only count ladder and two-player friendly battles, not Very Friendly or melee.
A rating difference around 200 (eg. one player has 1700 the other has 1500) suggests that there is an estimated 75% probability that the higher-ranked player will win. A difference of zero suggests an even chance. A difference of 500 suggests near certainty.
Unlike a proper Elo system, there is no initial ranking calculation - this means that a new player, if particularly strong or particularly weak, can destabilise people's scores a bit until their rank settles appropriately. Since everyone is equally effected by this, it doesn't really matter.
After each Elo-rated game, your score is updated according to this formula:
Rn = Ro + K(W - We)Rn : new rating
Ro : old rating
K : a constant, Warlocks uses 25
W : score; 1.0 for a kill, 0.9 for a defeat, 0.5 for a draw, 0.1 for a surrender, 0.0 for a death
We : expected score based on rank difference
The expected score follows a bell curve shape, such that the following table is approximately accurate:
|Elo difference||Expected score|
If your score is lower rather than higher, the expected score is one minus the given values, eg. an Elo lower by 677 means your expected score is 0.01, while your opponent's is 0.99.
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