Source description for demo by Trevor Norris.
/* jStat - Statistical Library * Copyright (c) 2010, Trevor Norris * This document is licensed as free software under the terms of the * MIT License: http://www.opensource.org/licenses/mit-license.php */ (function(Math,window){ var jStat = {}, sum = 'sum', min = 'min', max = 'max', mean = 'mean', median = 'median', range = 'range', variance = 'variance', stdev = 'stdev', quartiles = 'quartiles', covariance = 'covariance', corrcoeff = 'corrcoeff', Mmin = Math.min, Mmax = Math.max, Mfloor = Math.floor, Mpow = Math.pow, Msqrt = Math.sqrt, Mround = Math.round, arrSortF = function(a, b){ return a - b; }; /** * Sum of an array * @return {Number} * @param {Array} arr * @example * jStat.sum([1,2,3]) */ jStat[sum] = function(arr){ var sm = 0, i = arr.length - 1; for(; i >= 0; i--){ sm += arr[i]; }; return sm; }; /** * Minimum value of an array * @return {Number} * @param {Array} arr * @example * jStat.min([1,2,3]) */ jStat[min] = function(arr){ return Mmin.apply(Math,arr); }; /** * Maximum value of an array * @return {Number} * @param {Array} arr * @example * jStat.max([1,2,3]) */ jStat[max] = function(arr){ return Mmax.apply(Math,arr); }; /** * Mean value of an array * @return {Number} * @param {Array} arr * @example * jStat.mean([1,2,3]) */ jStat[mean] = function(arr){ return jStat[sum](arr) / arr.length; }; /** * Median of an array * @return {Number} * @param {Array} arr * @example * jStat.median([1,2,3,4,5,6]) */ jStat[median] = function(arr){ var arrlen = arr.length, _arr = arr.slice(0).sort(arrSortF); // Check if array is even or odd, then return the appropriate return !(arrlen & 1) ? (_arr[(arrlen / 2) - 1] + _arr[(arrlen / 2)]) / 2 : _arr[Mfloor(arrlen / 2)]; }; /** * Range of an array * @return {Number} * @param {Array} arr * @example * jStat.range([1,6,5,3,8,6]) */ jStat[range] = function(arr){ var _arr = arr.slice(0).sort(arrSortF); return _arr[_arr.length - 1] - _arr[0]; }; /** * Variance of an array * @return {Number} * @param {Array} arr * @example * jStat.variance([1,6,8,5,4,9,5,3]) */ jStat[variance] = function(arr){ var meen = jStat[mean](arr), stSum = 0, i = arr.length, arrlen = i; for(i--; i >= 0; i--){ stSum += Mpow((arr[i] - meen), 2); }; return stSum / (arrlen - 1); }; /** * Standard deviation of an array * @return {Number} * @param {Array} arr * @example * jStat.stdev([4,5,9,7,5,3,4]) */ jStat[stdev] = function(arr){ return Msqrt(jStat[variance](arr)); }; /** * Quartiles of an array * @return {Array} * @param {Array} arr * @example * jStat.quartiles([1,2,3,6,9,3,1,2,5]) */ jStat[quartiles] = function(arr){ var arrlen = arr.length, _arr = arr.slice(0).sort(arrSortF); return [_arr[Mround((arrlen) / 4) - 1], _arr[Mround((arrlen) / 2) - 1], _arr[Mround((arrlen) * 3 / 4) - 1]]; }; /** * Covariance of two arrays * @return {Number} * @param {Array} arr1 * @param {Array} arr2 * @example * jStat.covariance([1,2,3,6,9,3,1,2,5],[2,3,5,2,5,7,8,9,6]) */ jStat[covariance] = function(arr1, arr2){ var u = jStat[mean](arr1), v = jStat[mean](arr2), sq_dev = [], arr1Len = arr1.length, i = 0; for(; i < arr1Len; i++){ sq_dev[i] = (arr1[i] - u) * (arr2[i] - v); }; return jStat[sum](sq_dev) / arr1Len; }; /** * Correlation coefficient of two arrays * @return {Number} * @param {Array} arr1 * @param {Array} arr2 * @example * jStat.corrcoeff([1,2,3,6,9,3,1,2,5], [2,3,5,2,5,7,8,9,6]) */ jStat[corrcoeff] = function(arr1, arr2){ return jStat[covariance](arr1,arr2) / jStat[stdev](arr1) / jStat[stdev](arr2); }; // Exposing jStat window.jStat = jStat; })(Math,window);