Created
January 20, 2012 17:37
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Standard Deviation in Javascript
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// http://jsfiddle.net/hiddenloop/TPeJt/ | |
var array = [2, 3, 4, 6, 2, 5, 7, 2, 4, 5, 99]; | |
var within_std_of = 3; | |
outputResult = function(str) { | |
var content = $('#results').html(); | |
$('#results').html(content + str); | |
} | |
average = function(a) { | |
var r = {mean: 0, variance: 0, deviation: 0}, t = a.length; | |
for(var m, s = 0, l = t; l--; s += a[l]); | |
for(m = r.mean = s / t, l = t, s = 0; l--; s += Math.pow(a[l] - m, 2)); | |
return r.deviation = Math.sqrt(r.variance = s / t), r; | |
} | |
withinStd = function(mean, val, stdev) { | |
var low = mean-(stdev*x.deviation); | |
var hi = mean+(stdev*x.deviation); | |
return (val > low) && (val < hi); | |
} | |
outputResult("Set = [" + array.concat(',') + "]<br/><br/>"); | |
var x = average(array); | |
outputResult( | |
"mean = " + x.mean + "<br />" + | |
"deviation = " + x.deviation + "<br />" + | |
"variance = " + x.variance + "<br /><br />" | |
); | |
for(i=0; i<array.length; i++) { | |
outputResult (array[i] + " inside " + within_std_of + "std? <strong>" + withinStd(x.mean, array[i],within_std_of) + "</strong><br/>"); | |
} |
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