Metabolism: song as substrate, ecology grown from the track
A new top-level section building the metabolism concept: the track supplies the food field, event impulses and per-section laws; the seed picks the species (a rule set, not a parameter vector). Same song + seed => bit-identical frames; different songs => different worlds. - analysis: single FFT pass -> per-frame feature table; score (onsets folded into world geometry via voice ring + pitch-class sector), wells (food placed by the harmony), graph (band correlations -> interaction matrix), laws (per-section regimes) - sim: typed-array world, 3 castes (builder/orbit, forager/commute, spark/orbit-wide) with causality rings, persistence trails, consequence field; fully deterministic - lens: software framebuffer renderer (PNG in node, ImageData in browser) + event-reactive camera (cuts on activity change, alternating shot sizes, drift-and-push) - metrics: coupling x residual fitness (not per-frame descriptors) plus a grown-structure fingerprint; report + strip tools; 15 tests green - DESIGN.md captures the concept, invariants and build order 3 reference test signals (drone/runner/dusk) grow measurably distinct worlds while seeds of one song stay in the same biome.
This commit is contained in:
Dejvino
@@ -0,0 +1,410 @@
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// PCM -> per-frame feature table. Whole track, before the first frame renders.
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//
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// Nothing here reacts in realtime. The table is the song's score as numbers:
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// band energy, spectral flux, centroid, flatness, a dominant pitch, and the
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// places where the track changes. Everything downstream reads this table, so
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// preview and export cannot diverge.
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import { Fft, hann } from './fft.js';
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export const DEFAULT_FPS = 30;
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const BANDS = [
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[30, 160], // low — weight, pulse, foundation
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[160, 2000], // mid — body, voice, harmony
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[2000, 11000], // high — air, noise, detail
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];
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const clamp01 = (x) => (x < 0 ? 0 : x > 1 ? 1 : x);
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function percentile(values, p) {
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const a = Float32Array.from(values);
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a.sort();
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const i = Math.min(a.length - 1, Math.max(0, Math.round((a.length - 1) * p)));
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return a[i];
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}
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function normalise(series, loP = 0.03, hiP = 0.97) {
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const lo = percentile(series, loP);
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const hi = percentile(series, hiP);
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const k = hi - lo > 1e-9 ? 1 / (hi - lo) : 0;
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const out = new Float32Array(series.length);
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for (let i = 0; i < series.length; i++) out[i] = clamp01((series[i] - lo) * k);
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return out;
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}
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/** Local-maximum picking with an adaptive threshold. Returns discrete events. */
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export function pickOnsets(flux, fps, { minGap = 0.07, threshold = 1.35, window = 0.5 } = {}) {
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const n = flux.length;
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const w = Math.max(1, Math.round(window * fps));
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const gap = Math.max(1, Math.round(minGap * fps));
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const events = [];
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let sum = 0;
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for (let i = 0; i < n; i++) {
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sum += flux[i];
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if (i - w >= 0) sum -= flux[i - w];
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const mean = sum / Math.min(i + 1, w);
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if (i < 2 || i >= n - 1) continue;
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if (flux[i] <= flux[i - 1] || flux[i] < flux[i + 1]) continue;
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const floor = mean * threshold + 0.004;
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if (flux[i] < floor) continue;
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if (events.length && i - events[events.length - 1].frame < gap) {
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if (flux[i] > events[events.length - 1].strength) {
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events.pop();
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} else {
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continue;
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}
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}
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events.push({ frame: i, t: i / fps, strength: clamp01((flux[i] - floor) / Math.max(1e-6, 1 - floor)) });
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}
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return events;
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}
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/** Tempo from the onset envelope's autocorrelation. */
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function estimateTempo(onset, fps) {
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const minLag = Math.round((fps * 60) / 200);
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const maxLag = Math.round((fps * 60) / 50);
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let best = 0;
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let bestLag = 0;
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let total = 0;
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for (let i = 0; i < onset.length; i++) total += onset[i] * onset[i];
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for (let lag = minLag; lag <= maxLag; lag++) {
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let s = 0;
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for (let i = lag; i < onset.length; i++) s += onset[i] * onset[i - lag];
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s /= onset.length - lag;
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if (s > best) {
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best = s;
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bestLag = lag;
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}
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}
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if (!bestLag || total <= 1e-9) return { bpm: 0, beatStrength: 0 };
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// Normalised autocorrelation: a steady 4/4 lands well above 0.3, a drone
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// near 0.1. The sim uses strength, not bpm, to decide whether to march.
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return { bpm: (60 * fps) / bestLag, beatStrength: clamp01(best / (total / onset.length)) };
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}
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/**
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* Section boundaries: where the 4 Hz feature cloud changes its mind.
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* A boundary is a peak in the distance between the mean of the eight buckets
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* before it and the eight after it — cheap self-similarity, no FFT of the FFT.
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*/
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function findSections(frames4, fps4, duration) {
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const n = frames4.length;
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if (n < 8) return [{ start: 0, end: duration, index: 0 }];
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const half = 8;
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const novelty = new Float32Array(n);
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for (let i = half; i < n - half; i++) {
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let d = 0;
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for (let k = 0; k < 6; k++) {
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let a = 0;
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let b = 0;
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for (let j = 1; j <= half; j++) {
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a += frames4[i - j][k];
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b += frames4[i + j][k];
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}
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d += ((a - b) / half) ** 2;
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}
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novelty[i] = Math.sqrt(d);
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}
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const peak = Math.max(...novelty);
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if (peak <= 1e-8) return [{ start: 0, end: duration, index: 0 }];
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for (let i = 0; i < n; i++) novelty[i] /= peak;
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const minGap = Math.round(10 * fps4);
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const accepted = [];
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const guard = Math.round(4 * fps4);
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for (let i = guard; i < n - guard; i++) {
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if (novelty[i] < 0.45) continue;
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if (novelty[i] < novelty[i - 1] || novelty[i] < novelty[i + 1]) continue;
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if (accepted.length && i - accepted[accepted.length - 1] < minGap) {
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if (novelty[i] > novelty[accepted[accepted.length - 1]]) accepted.pop();
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else continue;
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}
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accepted.push(i);
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if (accepted.length >= 6) break;
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}
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let cuts = [0, ...accepted.map((i) => i / fps4), duration];
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// Absorb sections shorter than four seconds: a boundary that survives for
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// two seconds is a swell, not an era. The sim cannot change laws that fast.
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cuts = cuts.filter((c, i) => i === 0 || i === cuts.length - 1 || c - cuts[i - 1] >= 4);
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const sections = [];
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for (let i = 0; i < cuts.length - 1; i++) {
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if (cuts[i + 1] - cuts[i] < 1.5) continue;
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sections.push({ start: cuts[i], end: cuts[i + 1], index: sections.length });
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}
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if (!sections.length) return [{ start: 0, end: duration, index: 0 }];
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return sections;
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}
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function classifySections(sections, energyAt) {
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const es = sections.map((s) => energyAt(s));
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const sorted = [...es].sort((a, b) => a - b);
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const p20 = sorted[Math.floor(sorted.length * 0.2)];
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const p50 = sorted[Math.floor(sorted.length * 0.5)];
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const p80 = sorted[Math.floor(sorted.length * 0.8)];
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const kinds = sections.map((s, i) => {
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const e = es[i];
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const prev = es[i - 1] ?? e;
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if (i === 0 && e <= p50) return 'intro';
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if (i === sections.length - 1 && e <= p50) return 'outro';
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if (e >= p80) return 'drop';
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if (e <= p20) return 'breakdown';
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if (e > prev + 0.04) return 'build';
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return 'sustain';
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});
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return sections.map((s, i) => ({
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...s,
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kind: kinds[i],
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energy: es[i],
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centroid: s.centroid,
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flatness: s.flatness,
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}));
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}
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/**
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* @param {Float32Array} samples mono
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* @param {number} sampleRate
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* @param {{fps?:number, fftSize?:number}} options
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*/
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export function analyse(samples, sampleRate, { fps = DEFAULT_FPS, fftSize = 2048 } = {}) {
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const duration = samples.length / sampleRate;
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const frames = Math.max(1, Math.floor(duration * fps));
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const hop = sampleRate / fps;
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const fft = new Fft(fftSize);
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const win = hann(fftSize);
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const re = new Float32Array(fftSize);
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const im = new Float32Array(fftSize);
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const mag = new Float32Array(fftSize / 2);
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const prevMag = new Float32Array(fftSize / 2);
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const nyquist = sampleRate / 2;
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const binHz = nyquist / (fftSize / 2);
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const bandBins = BANDS.map(([lo, hi]) => [
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Math.max(1, Math.floor(lo / binHz)),
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Math.min(fftSize / 2 - 1, Math.ceil(hi / binHz)),
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]);
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const energyRaw = new Float32Array(frames);
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const bandsRaw = [new Float32Array(frames), new Float32Array(frames), new Float32Array(frames)];
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const fluxRaw = new Float32Array(frames);
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const bandFluxRaw = [new Float32Array(frames), new Float32Array(frames), new Float32Array(frames)];
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const centroidRaw = new Float32Array(frames);
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const flatnessRaw = new Float32Array(frames);
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const dominantRaw = new Float32Array(frames);
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const chroma = new Float32Array(12);
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for (let f = 0; f < frames; f++) {
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const start = Math.min(samples.length - fftSize, Math.floor(f * hop));
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let rms = 0;
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for (let i = 0; i < fftSize; i++) {
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const s = start + i >= 0 ? samples[start + i] || 0 : 0;
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re[i] = s * win[i];
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im[i] = 0;
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rms += s * s;
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}
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energyRaw[f] = Math.sqrt(rms / fftSize);
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fft.forward(re, im);
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let sumP = 0;
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let sumLog = 0;
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let weighted = 0;
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let peakBin = 1;
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let peakMag = 0;
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let flux = 0;
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for (let b = 1; b < fftSize / 2; b++) {
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const m = Math.sqrt(re[b] * re[b] + im[b] * im[b]) / (fftSize / 2);
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mag[b] = m;
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const p = m * m + 1e-12;
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sumP += p;
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sumLog += Math.log(p);
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weighted += b * binHz * p;
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if (m > peakMag) {
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peakMag = m;
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peakBin = b;
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}
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const hz = b * binHz;
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if (hz > 45 && hz < 2400) {
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const semis = Math.round(12 * Math.log2(hz / 440));
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const pc = ((semis % 12) + 12 + 9) % 12;
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chroma[pc] += m * m;
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}
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flux += Math.max(0, m - prevMag[b]);
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}
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const count = fftSize / 2 - 1;
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// Log-frequency centroid: 50 Hz -> 0, Nyquist -> 1. A linear Hz centroid
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// sits near 0.02 for every real track and cannot tell dark from bright.
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const meanHz = weighted / Math.max(sumP, 1e-12);
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centroidRaw[f] = clamp01(Math.log2(Math.max(50, meanHz) / 50) / Math.log2(nyquist / 50));
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flatnessRaw[f] = sumP > 1e-8 ? clamp01((Math.exp(sumLog / count) / (sumP / count)) * 20) : 0;
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fluxRaw[f] = Math.min(1, flux * 4);
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dominantRaw[f] = peakBin * binHz;
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for (let k = 0; k < 3; k++) {
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const [lo, hi] = bandBins[k];
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let e = 0;
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let fl = 0;
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for (let b = lo; b <= hi; b++) {
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const m = mag[b];
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e += m * m;
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fl += Math.max(0, m - prevMag[b]);
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}
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bandsRaw[k][f] = Math.sqrt(e / (hi - lo + 1));
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bandFluxRaw[k][f] = Math.min(1, fl * 4);
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}
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prevMag.set(mag);
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}
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const energy = normalise(energyRaw);
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const low = normalise(bandsRaw[0]);
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const mid = normalise(bandsRaw[1]);
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const high = normalise(bandsRaw[2]);
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const flux = normalise(fluxRaw);
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const bandFlux = bandFluxRaw.map((s) => normalise(s));
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const onsets = bandFlux.map((s, k) => pickOnsets(s, fps, { threshold: k === 2 ? 1.5 : 1.3 }));
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const combined = new Float32Array(frames);
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for (let i = 0; i < frames; i++) combined[i] = Math.max(bandFlux[0][i], bandFlux[1][i] * 0.8, bandFlux[2][i] * 0.5);
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const allOnsets = mergeOnsets(onsets, fps);
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const tempo = estimateTempo(combined, fps);
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// 4 Hz section view.
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const fps4 = Math.min(fps, 4);
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const per = fps / fps4;
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const frames4 = [];
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for (let i = 0; i * per < frames; i++) {
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const a = Math.floor(i * per);
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const b = Math.min(frames, Math.floor((i + 1) * per));
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const row = [0, 0, 0, 0, 0, 0];
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for (let j = a; j < b; j++) {
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row[0] += energy[j];
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row[1] += low[j];
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row[2] += mid[j];
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row[3] += high[j];
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row[4] += centroidRaw[j];
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row[5] += flux[j];
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}
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const k = 1 / Math.max(1, b - a);
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frames4.push(row.map((v) => v * k));
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}
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const rawSections = findSections(frames4, fps4, duration);
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const sections = classifySections(rawSections, (s) => {
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const a = Math.floor(s.start * fps);
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const b = Math.max(a + 1, Math.floor(s.end * fps));
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let sum = 0;
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for (let i = a; i < b; i++) sum += energy[i];
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return sum / (b - a);
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}).map((s) => {
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const a = Math.floor(s.start * fps);
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const b = Math.max(a + 1, Math.floor(s.end * fps));
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let c = 0;
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let fl = 0;
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for (let i = a; i < b; i++) {
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c += centroidRaw[i];
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fl += flatnessRaw[i];
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}
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return { ...s, centroid: c / (b - a), flatness: fl / (b - a) };
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});
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const bandCorrelation = correlate3([low, mid, high]);
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const dynamicRange = Math.max(0, percentile(energyRaw, 0.96) - percentile(energyRaw, 0.1)) /
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Math.max(1e-9, percentile(energyRaw, 0.96));
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let key = 0;
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let keyEnergy = 0;
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const chromaPeak = Math.max(...chroma);
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for (let i = 0; i < 12; i++) {
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if (chroma[i] > keyEnergy) {
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keyEnergy = chroma[i];
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key = i;
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}
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}
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const chromaNorm = Array.from(chroma, (v) => (chromaPeak > 1e-9 ? v / chromaPeak : 0));
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const summary = {
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duration,
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bpm: tempo.bpm,
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beatStrength: tempo.beatStrength,
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centroid: mean(centroidRaw),
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flatness: mean(flatnessRaw),
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dynamics: clamp01(dynamicRange),
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loudness: mean(energyRaw),
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onsetDensity: allOnsets.length / Math.max(1, duration),
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bandBalance: [mean(low), mean(mid), mean(high)],
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bandCorrelation,
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chroma: chromaNorm,
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key,
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sections: sections.length,
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kinds: sections.map((s) => s.kind),
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};
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return {
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fps,
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frames,
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duration,
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sampleRate,
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bands: { low, mid, high },
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bandFlux,
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energy,
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flux,
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centroid: centroidRaw,
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flatness: flatnessRaw,
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dominantHz: dominantRaw,
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onsets: { low: onsets[0], mid: onsets[1], high: onsets[2], all: allOnsets },
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sections,
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summary,
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};
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}
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function mean(a) {
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let s = 0;
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for (let i = 0; i < a.length; i++) s += a[i];
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return s / Math.max(1, a.length);
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}
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/**
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* One event per moment. Bands fire together on a transient; three simultaneous
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* events would triple the food at the same instant. Keep the strongest, at
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* least 120 ms apart, and carry the voice so the world knows what spoke.
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*/
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function mergeOnsets(bandOnsets, fps, minGap = 0.12) {
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const all = [];
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for (let voice = 0; voice < bandOnsets.length; voice++) {
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for (const o of bandOnsets[voice]) all.push({ ...o, voice });
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}
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all.sort((a, b) => a.frame - b.frame || b.strength - a.strength);
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const gap = Math.max(1, Math.round(minGap * fps));
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const out = [];
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for (const e of all) {
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const last = out[out.length - 1];
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if (last && e.frame - last.frame < gap) {
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if (e.strength > last.strength) out[out.length - 1] = e;
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continue;
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}
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out.push(e);
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}
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return out;
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}
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function correlate3(series) {
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const out = [[1, 0, 0], [0, 1, 0], [0, 0, 1]];
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for (let i = 0; i < 3; i++) {
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for (let j = i + 1; j < 3; j++) {
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||||
const a = series[i];
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const b = series[j];
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const ma = mean(a);
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const mb = mean(b);
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let num = 0;
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let da = 0;
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let db = 0;
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for (let k = 0; k < a.length; k++) {
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const x = a[k] - ma;
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const y = b[k] - mb;
|
||||
num += x * y;
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||||
da += x * x;
|
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db += y * y;
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}
|
||||
const r = num / Math.sqrt(Math.max(1e-12, da * db));
|
||||
out[i][j] = r;
|
||||
out[j][i] = r;
|
||||
}
|
||||
}
|
||||
return out;
|
||||
}
|
||||
Reference in New Issue
Block a user