86 lines
2.6 KiB
JavaScript
86 lines
2.6 KiB
JavaScript
/**
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* Line shopping — for each unique prop (game/player/stat), find the best
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* line per side across books.
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*
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* Best Over = lowest line + best odds at that line.
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* Best Under = highest line + best odds at that line.
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*
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* We also flag "outlier" books — a book that's 1+ points off the median.
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*/
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function propKey(p) {
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return `${p.game_id}|${p.player_id ?? p.player_name}|${p.stat_type}`;
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}
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function americanToImplied(odds) {
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if (typeof odds !== 'number' || !Number.isFinite(odds)) return null;
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return odds > 0 ? 100 / (odds + 100) : -odds / (-odds + 100);
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}
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function median(values) {
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if (!values.length) return null;
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const sorted = [...values].sort((a, b) => a - b);
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const mid = Math.floor(sorted.length / 2);
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return sorted.length % 2 ? sorted[mid] : (sorted[mid - 1] + sorted[mid]) / 2;
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}
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function process(props) {
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const grouped = new Map();
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for (const p of props || []) {
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const key = propKey(p);
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if (!grouped.has(key)) grouped.set(key, []);
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grouped.get(key).push(p);
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}
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const out = [];
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for (const [key, rows] of grouped.entries()) {
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if (rows.length === 1) {
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out.push({ ...rows[0], best_over: rows[0], best_under: rows[0], line_outliers: [] });
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continue;
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}
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const lines = rows.map((r) => r.line).filter((n) => typeof n === 'number');
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const med = median(lines);
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const overs = rows.filter((r) => r.odds_over != null);
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const unders = rows.filter((r) => r.odds_under != null);
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// Best Over = lowest line, then best (highest implied prob) odds at that line.
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let bestOver = null;
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for (const r of overs) {
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if (!bestOver) { bestOver = r; continue; }
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if (r.line < bestOver.line) bestOver = r;
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else if (r.line === bestOver.line) {
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const a = americanToImplied(r.odds_over);
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const b = americanToImplied(bestOver.odds_over);
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if (a != null && b != null && a < b) bestOver = r;
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}
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}
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let bestUnder = null;
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for (const r of unders) {
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if (!bestUnder) { bestUnder = r; continue; }
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if (r.line > bestUnder.line) bestUnder = r;
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else if (r.line === bestUnder.line) {
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const a = americanToImplied(r.odds_under);
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const b = americanToImplied(bestUnder.odds_under);
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if (a != null && b != null && a < b) bestUnder = r;
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}
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}
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const outliers = (med != null)
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? rows.filter((r) => Math.abs(r.line - med) >= 1).map((r) => ({ book: r.book, line: r.line, delta: r.line - med }))
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: [];
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out.push({
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key,
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median_line: med,
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books: rows,
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best_over: bestOver,
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best_under: bestUnder,
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line_outliers: outliers,
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});
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}
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return out;
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}
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module.exports = { process, americanToImplied };
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