{"id":292,"date":"2011-03-06T13:40:01","date_gmt":"2011-03-06T19:40:01","guid":{"rendered":"http:\/\/bateru.com\/news\/?p=292"},"modified":"2012-11-22T02:50:55","modified_gmt":"2012-11-22T08:50:55","slug":"javascript-standard-deviation-variance-average-functions","status":"publish","type":"post","link":"https:\/\/bateru.com\/news\/2011\/03\/javascript-standard-deviation-variance-average-functions\/","title":{"rendered":"Javascript Standard Deviation, Variance, Average functions."},"content":{"rendered":"

Hey everyone,
\nI just installed WP-Syntax<\/a> for the WordPress and I want to test it out by posting javascript code for finding Standard Deviation, Variance, Average among numbers.<\/p>\n

Without WP-Syntax<\/b>
\n
\nvar str = 'This is a string.';
\nconsole.log( str ); \/\/Boring!
\n<\/code><\/p>\n

With WP-Syntax<\/b><\/p>\n

\r\nvar str = 'hello world. Here I am!';\r\nconsole.log( str ); \/\/Nice colors!!\r\n<\/pre>\n
Without more delay, here are the Statistics functions.<\/p>\n
Code<\/h2>\n
\r\n\/\/ Programmer: Larry Battle \r\n\/\/ Date: Mar 06, 2011\r\n\/\/ Purpose: Calculate standard deviation, variance, and average among an array of numbers.\r\nvar isArray = function (obj) {\r\n\treturn Object.prototype.toString.call(obj) === \"[object Array]\";\r\n},\r\ngetNumWithSetDec = function( num, numOfDec ){\r\n\tvar pow10s = Math.pow( 10, numOfDec || 0 );\r\n\treturn ( numOfDec ) ? Math.round( pow10s * num ) \/ pow10s : num;\r\n},\r\ngetAverageFromNumArr = function( numArr, numOfDec ){\r\n\tif( !isArray( numArr ) ){ return false;\t}\r\n\tvar i = numArr.length, \r\n\t\tsum = 0;\r\n\twhile( i-- ){\r\n\t\tsum += numArr[ i ];\r\n\t}\r\n\treturn getNumWithSetDec( (sum \/ numArr.length ), numOfDec );\r\n},\r\ngetVariance = function( numArr, numOfDec ){\r\n\tif( !isArray(numArr) ){ return false; }\r\n\tvar avg = getAverageFromNumArr( numArr, numOfDec ), \r\n\t\ti = numArr.length,\r\n\t\tv = 0;\r\n\t\t\r\n\twhile( i-- ){\r\n\t\tv += Math.pow( (numArr[ i ] - avg), 2 );\r\n\t}\r\n\tv \/= numArr.length;\r\n\treturn getNumWithSetDec( v, numOfDec );\r\n},\r\ngetStandardDeviation = function( numArr, numOfDec ){\r\n\tif( !isArray(numArr) ){ return false; }\r\n\tvar stdDev = Math.sqrt( getVariance( numArr, numOfDec ) );\r\n\treturn getNumWithSetDec( stdDev, numOfDec );\r\n};\r\n<\/pre>\n
Usage<\/h2>\n
Testing with numbers from wiki<\/a><\/p>\n
\r\nvar arrOfNums = [ 2,4,4,4,5,5,7,9 ],\r\n\tprecision = 4;\r\n\t\r\ngetAverageFromNumArr( arrOfNums, precision );\t\/\/returns 5\r\ngetVariance( arrOfNums, precision );\t\/\/ returns 4\r\ngetStandardDeviation( arrOfNums, precision ); \/\/returns 2\r\n<\/pre>\n
Enjoy! \ud83d\ude42
\nUpdate<\/b>
\nFor those wanting more statistical functions, use jStat : a JavaScript statistical library.<\/a> by John Resig<\/a>.<\/p>\n
\n
jStat<\/a> is a statistical library written in JavaScript that allows you to perform advanced statistical operations without the need of a dedicated statistical language (i.e. MATLAB or R).\n<\/p><\/blockquote>\n
Update 2<\/b>
\nPlease read this for more information “http:\/\/easycalculation.com\/statistics\/learn-standard-deviation.php”<\/a><\/p>\n