locutus/python/statistics/variance.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.variance = variance;
function variance(data, xbar) {
    //      discuss at: https://locutus.io/python/statistics/variance/
    // parity verified: Python 3.12
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Returns the sample variance and preserves exact integer results when Python does.
    //       example 1: variance([1, 2, 3])
    //       returns 1: 1
    //       example 2: variance([1, 3])
    //       returns 2: 2
    //       example 3: variance([1, 2, 3], 2)
    //       returns 3: 1
    const sequence = toNumericSequence(data, 'variance');
    if (sequence.values.length < 2) {
        throw new Error('variance requires at least two data points');
    }
    return statisticsVarianceFromSequence(sequence, sequence.values.length - 1, 'variance', xbar);
}
function toNumericSequence(data, functionName) {
    const values = assertStatisticsArray(data, functionName);
    return {
        values: values.map((value) => toStatisticNumber(value, functionName)),
        integral: values.every(isIntegralStatisticValue),
    };
}
function statisticsVarianceFromSequence(sequence, divisor, functionName, center) {
    const mean = center === undefined ? statisticsMeanFromSequence(sequence) : toStatisticNumber(center, functionName);
    const squaredDeltaSum = sequence.values.reduce((sum, value) => {
        const delta = value - mean;
        return sum + delta * delta;
    }, 0);
    return divideStatisticsValue(squaredDeltaSum, divisor, sequence.integral);
}
function statisticsMeanFromSequence(sequence) {
    return divideStatisticsValue(sumNumbers(sequence.values), sequence.values.length, sequence.integral);
}
function assertStatisticsArray(data, functionName) {
    if (!Array.isArray(data)) {
        throw new TypeError(`${functionName}() data must be an array`);
    }
    return data;
}
function toStatisticNumber(value, functionName) {
    if (typeof value === 'number') {
        return value;
    }
    if (typeof value === 'boolean') {
        return value ? 1 : 0;
    }
    if (typeof value === 'bigint') {
        const numericValue = Number(value);
        if (!Number.isSafeInteger(numericValue)) {
            throw new RangeError(`${functionName}() bigint values must fit within JS safe integers`);
        }
        return numericValue;
    }
    throw new TypeError(`${functionName}() data must contain only real numbers`);
}
function isIntegralStatisticValue(value) {
    return (typeof value === 'boolean' || typeof value === 'bigint' || (typeof value === 'number' && Number.isInteger(value)));
}
function sumNumbers(values) {
    return values.reduce((sum, value) => sum + value, 0);
}
function divideStatisticsValue(total, divisor, integral) {
    if (integral && Number.isSafeInteger(total) && total % divisor === 0) {
        return total / divisor;
    }
    return total / divisor;
}