JS版一元线性回归

<script language="JavaScript">

    Array.prototype.Average = function (value){
        var i;
        var avg=0;
        var sum=0;
        for (i=0; i < this.length; i++) {
            sum += this[i];
        }
        avg = sum/this.length
        return avg;
    }

    var xNum = new Array(187.1,179.5,157.0,197.0,239.4,217.8,227.1,233.4,242.0,251.9,230.0,271.8);
    var yNum = new Array(25.4,22.8,20.6,21.8,32.4,24.4,29.3,27.9,27.8,34.2,29.2,30.0);
    xa = xNum.Average();
    ya = yNum.Average();
    
    var Lxx = 0;
    var Lxy = 0;
    for(i=0;i<xNum.length;i++){
        Lxx += ((xNum[i]-xa)*(xNum[i]-xa));
        Lxy += ((xNum[i]-xa)*(yNum[i]-ya));
    }
    
    var a = new Number();
    var b = new Number();
    b = Lxy/Lxx;
    a = ya - b*xa;
    
    document.write("Y="+b.toFixed(1)+"*X"+"+"+a.toFixed(1));
    
    
</script>