@naturalcycles/js-lib/dist/math/math.util.js

Standard library for universal (browser + Node.js) javascript

import { _assert } from '../error/assert.js';
import { _sortNumbers } from '../number/number.util.js';
/**
 * @returns Average of the array of numbers
 *
 * @example
 *
 * _average([1, 2, 3, 4])
 * // 2.5
 */
export function _average(values) {
    _assert(values.length, '_average is called on empty array');
    let total = 0;
    for (const n of values)
        total += n;
    return total / values.length;
}
/**
 * Same as _average, but safely returns null if input array is empty or nullish.
 */
export function _averageOrNull(values) {
    return values?.length ? _average(values) : null;
}
/**
 * valuesArray and weightsArray length is expected to be the same.
 */
export function _averageWeighted(values, weights) {
    let numerator = 0;
    let denominator = 0;
    for (let i = 0; i < values.length; i++) {
        numerator += values[i] * weights[i];
        denominator += weights[i];
    }
    return numerator / denominator;
}
/**
 * @example
 *
 * _percentile([1, 2, 3, 4], 50)
 * // 2.5
 *
 * _percentile([1, 2, 3], 50)
 * // 2
 *
 * _percentile([1, 2, 3], 100)
 * // 3
 */
export function _percentile(values, pc) {
    const sorted = _sortNumbers(values);
    // Floating pos in the range of [0; length - 1]
    const pos = ((values.length - 1) * pc) / 100;
    const dec = pos % 1;
    const floorPos = Math.floor(pos);
    const ceilPos = Math.ceil(pos);
    return _averageWeighted([sorted[floorPos], sorted[ceilPos]], [1 - dec, dec]);
}
/**
 * A tiny bit more efficient function than calling _percentile individually.
 */
export function _percentiles(values, pcs) {
    const r = {};
    const sorted = _sortNumbers(values);
    for (const pc of pcs) {
        // Floating pos in the range of [0; length - 1]
        const pos = ((values.length - 1) * pc) / 100;
        const dec = pos % 1;
        const floorPos = Math.floor(pos);
        const ceilPos = Math.ceil(pos);
        r[pc] = _averageWeighted([sorted[floorPos], sorted[ceilPos]], [1 - dec, dec]);
    }
    return r;
}
/**
 * @example
 *
 * _median([1, 2, 3])
 * // 2
 *
 * _median([1, 2, 3, 4])
 * // 2.5
 */
export function _median(values) {
    return _percentile(values, 50);
}