TypeScript Port of http://clauswitt.com/simple-statistics-in-javascript.html ( https://gist.github.com/clauswitt/1285478 )

Stats.ts

module hist.utils {


    // TypeScript Port of http://clauswitt.com/simple-statistics-in-javascript.html
    // https://gist.github.com/clauswitt/1285478

    // Use:
    // var stats = new hist.utils.Stats( [ 1 , 2 , 3 , 4 , 5 , 6 ] );
    // stats.getArithmeticMean();
    // stats.getGeometricMean();


    export class Stats {

        private a:number[];

        constructor( arr:number[] ){
            this.a = arr || [];
        }
        
        //http://en.wikipedia.org/wiki/Mean#Arithmetic_mean_.28AM.29
        getArithmeticMean():number {
            var sum = 0;
            var length = this.a.length;
            for( var i=0; i<length; i++ ){
                sum += this.a[ i ];
            }
            return sum/length;
        }
        
        //http://en.wikipedia.org/wiki/Mean#Geometric_mean_.28GM.29
        getGeometricMean():number {
            var product = 1;
            var length = this.a.length; 
            for( var i=0; i<length; i++ ){
                product = product * this.a[ i ];
            }
            return Math.pow( product , ( 1/length ) );
        }
        
        //http://en.wikipedia.org/wiki/Mean#Harmonic_mean_.28HM.29
        getHarmonicMean():number {
            var sum = 0;
            var length = this.a.length; 
            for( var i = 0; i < length; i++ ){
                sum += ( 1 / this.a[ i ] );
            }
            return length/sum;
        }
        
        //http://en.wikipedia.org/wiki/Standard_deviation
        getStandardDeviation():number {
            var arithmeticMean = this.getArithmeticMean(); 
            var sum = 0
            var length = this.a.length; 
            for( var i = 0; i < length; i++ ){
                sum += Math.pow( this.a[ i ] - arithmeticMean , 2 );
            }
            return Math.pow( sum / length , 0.5 );
        }
        
        //http://en.wikipedia.org/wiki/Median
        getMedian():number {
            var length = this.a.length; 
            var middleId = Math.floor( length / 2 );
            var arr = this.a.sort( this.sort );
            return arr[ middleId ];
        }
        
        setArray( arr:number[] ){
            this.a = arr; 
            return self; 
        }
        
        getArray():number[] {
            return this.a; 
        }

        private sort( a , b ){
            return a - b;
        }

    }
}