19 lines
598 B
JavaScript
19 lines
598 B
JavaScript
const elo = ([...ratings], kFactor = 32, selfRating) => {
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const [a, b] = ratings;
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const expectedScore = (self, opponent) => 1 / (1 + 10 ** ((opponent - self) / 400));
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const newRating = (rating, i) =>
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(selfRating || rating) + kFactor * (i - expectedScore(i ? a : b, i ? b : a));
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if (ratings.length === 2)
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return [newRating(a, 1), newRating(b, 0)];
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for (let i = 0, len = ratings.length; i < len; i++) {
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let j = i;
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while (j < len - 1) {
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j++;
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[ratings[i], ratings[j]] = elo([ratings[i], ratings[j]], kFactor);
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}
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}
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return ratings;
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};
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module.exports = elo;
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