dsp-collection/signal/Autocorrelation.js

A collection of JavaScript modules for digital signal processing (written in TypeScript)

import * as WindowFunctions from "./WindowFunctions.js";
import * as ArrayUtils from "../utils/ArrayUtils.js";
function autocorrelationKernel(x, distance, n) {
    let sum = 0;
    for (let i = 0; i < n; i++) {
        sum += x[i] * x[i + distance];
    }
    return sum;
}
export function nonPeriodicAutocorrelationSingle(x, distance, compensate) {
    const n = x.length - distance;
    let sum = autocorrelationKernel(x, distance, n);
    if (compensate && n > 0) {
        sum *= x.length / n;
    }
    return sum;
}
export function findNonPeriodicAutocorrelationMaximum(x, minDistance, maxDistance, fixedOverlapWidth) {
    let maxVal = -Infinity;
    let maxPos = minDistance;
    for (let distance = minDistance; distance < maxDistance; distance++) {
        const val = fixedOverlapWidth ?
            autocorrelationKernel(x, distance, x.length - maxDistance) :
            nonPeriodicAutocorrelationSingle(x, distance, true);
        if (val > maxVal) {
            maxVal = val;
            maxPos = distance;
        }
    }
    return maxPos;
}
export function nonPeriodicAutocorrelation(x, normalize) {
    const n = x.length;
    const r = new Float64Array(n);
    for (let distance = 0; distance < n; distance++) {
        r[distance] = nonPeriodicAutocorrelationSingle(x, distance, true);
    }
    if (normalize && n > 0 && r[0] != 0) {
        const max = r[0];
        for (let distance = 0; distance < n; distance++) {
            r[distance] /= max;
        }
    }
    return r;
}
export function windowedNonPeriodicAutocorrelation(x, windowFunction, normalize) {
    const windowed = WindowFunctions.applyWindow(x, windowFunction);
    const autoCorr = nonPeriodicAutocorrelation(windowed, normalize);
    const window = WindowFunctions.getWindowTable(windowFunction, x.length);
    const windowAutoCorr = nonPeriodicAutocorrelation(window, true);
    const compensated = ArrayUtils.divide(autoCorr, windowAutoCorr);
    return compensated;
}
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