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clauswitt/Stats.js

Created October 13, 2011 20:47
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Simple statistics for javascript
Raw
Stats.js
function Stats(arr) {
var self = this;
var theArray = arr || [];
//http://en.wikipedia.org/wiki/Mean#Arithmetic_mean_.28AM.29
self.getArithmeticMean = function() {
var sum = 0, length = theArray.length;
for(var i=0;i<length;i++) {
sum += theArray[i];
}
return sum/length;
}
//http://en.wikipedia.org/wiki/Mean#Geometric_mean_.28GM.29
self.getGeometricMean = function() {
var product = 1, length = theArray.length;
for(var i=0;i<length;i++) {
product = product * theArray[i];
}
return Math.pow(product,(1/length));
}
//http://en.wikipedia.org/wiki/Mean#Harmonic_mean_.28HM.29
self.getHarmonicMean = function() {
var sum = 0, length = theArray.length;
for(var i=0;i<length;i++) {
sum += (1/theArray[i]);
}
return length/sum;
}
//http://en.wikipedia.org/wiki/Standard_deviation
self.getStandardDeviation = function() {
var arithmeticMean = this.getArithmeticMean();
var sum = 0, length = theArray.length;
for(var i=0;i<length;i++) {
sum += Math.pow(theArray[i]-arithmeticMean, 2);
}
return Math.pow(sum/length, 0.5);
}
//http://en.wikipedia.org/wiki/Median
self.getMedian = function() {
var length = theArray.length;
var middleValueId = Math.floor(length/2);
var arr = theArray.sort(function(a, b){return a-b;});
return arr[middleValueId];
}
self.setArray = function(arr) {
theArray = arr;
return self;
}
self.getArray = function() {
return theArray;
}
return self;
}
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