timesync/lib/stat.js

Time synchronization between peers

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.add = add;
exports.compare = compare;
exports.mean = mean;
exports.median = median;
exports.std = std;
exports.sum = sum;
exports.variance = variance;

// basic statistical functions
function compare(a, b) {
  return a > b ? 1 : a < b ? -1 : 0;
}

function add(a, b) {
  return a + b;
}

function sum(arr) {
  return arr.reduce(add);
}

function mean(arr) {
  return sum(arr) / arr.length;
}

function std(arr) {
  return Math.sqrt(variance(arr));
}

function variance(arr) {
  if (arr.length < 2) return 0;

  var _mean = mean(arr);

  return arr.map(function (x) {
    return Math.pow(x - _mean, 2);
  }).reduce(add) / (arr.length - 1);
}

function median(arr) {
  if (arr.length < 2) return arr[0];
  var sorted = arr.slice().sort(compare);

  if (sorted.length % 2 === 0) {
    // even
    return (sorted[arr.length / 2 - 1] + sorted[arr.length / 2]) / 2;
  } else {
    // odd
    return sorted[(arr.length - 1) / 2];
  }
}