wilson-interval-func/src/index.js

Calculate pearson correlation rank

import pnormaldist from 'pnormaldist';

export default class WilsonInterval  {

    /**
     *
     * @param positiveVotes
     * @param totalVotes
     * @returns {number}
     */
    static calc(positiveVotes, totalVotes) {
        const z = pnormaldist(1 - (1 - WilsonInterval.CONFIDENCE) / 2);
        return totalVotes ? WilsonInterval.lowerBound(positiveVotes, totalVotes, z) : 0;
    }

    /**
     *
     * @param positiveVotes
     * @param totalVotes
     * @param confidence
     * @returns {number}
     */
    static lowerBound(positiveVotes, totalVotes, confidence)
    {
        const phat = 1.0 * positiveVotes / totalVotes,
            numerator = WilsonInterval.calcNumerator(totalVotes, confidence, phat),
            denominator = WilsonInterval.calcDenominator(totalVotes, confidence);

        return numerator / denominator;
    }

    /**
     *
     * @param total
     * @param z
     * @returns {number}
     */
    static calcDenominator(total, z)
    {
        return 1 + z * z / total;
    }

    /**
     *
     * @param total
     * @param z
     * @param phat
     * @returns {number}
     */
    static calcNumerator(total, z, phat)
    {
        return phat + z * z / (2 * total) - z * Math.sqrt((phat * (1 - phat) + z * z / (4 * total)) / total);
    }

    /**
     *
     * @returns {number}
     * @constructor
     */
    static get CONFIDENCE() {
        return .975;
    }
}

module.exports = WilsonInterval;