@codibre/fluent-iterable/dist/utils/get-stats-stepper.js

Provides LINQ-like fluent api operations for iterables and async iterables (ES2018+).

"use strict";
var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
exports.getMinMaxStepper = getMinMaxStepper;
exports.getStatsStepper = getStatsStepper;
const utils_1 = require("./utils");
const fluent_1 = __importDefault(require("../fluent"));
const SQUARE = 2;
function getMinMaxStepper() {
    let min = Number.POSITIVE_INFINITY;
    let max = Number.NEGATIVE_INFINITY;
    const wrapper = {
        get min() {
            return min;
        },
        get max() {
            return max;
        },
        step(y) {
            if (min > y)
                min = y;
            if (max < y)
                max = y;
            return y;
        },
    };
    return wrapper;
}
/**
 * Stepper to calculate many statistical measures, like
 * min, max, population standard deviation, population variance,
 * sample standard deviation and sample variance
 */
function getStatsStepper() {
    const avgStepper = (0, utils_1.getAverageStepper)();
    const minMaxStepper = getMinMaxStepper();
    let variance;
    let lastVarianceCount = 0;
    const items = [];
    const wrapper = {
        get avg() {
            return avgStepper.avg;
        },
        get count() {
            return avgStepper.count;
        },
        get min() {
            return minMaxStepper.min;
        },
        get max() {
            return minMaxStepper.max;
        },
        get populationVariance() {
            if (variance === undefined || lastVarianceCount !== avgStepper.count) {
                variance = (0, fluent_1.default)(items)
                    .map((x) => (x - avgStepper.avg) ** SQUARE)
                    .avg();
                lastVarianceCount = avgStepper.count;
            }
            return variance;
        },
        get populationStdDev() {
            return Math.sqrt(this.populationVariance);
        },
        get sampleVariance() {
            return ((this.populationVariance * avgStepper.count) / (avgStepper.count - 1));
        },
        get sampleStdDev() {
            return Math.sqrt(this.sampleVariance);
        },
        step: (y) => {
            items.push(y);
            avgStepper.step(y);
            return minMaxStepper.step(y);
        },
    };
    return wrapper;
}