Method variance

JSAT/src/jsat/linear/Vec.java:526–544

Computes the variance of the values in this vector, which is #standardDeviation() 2 @return the variance

()

     * @return the variance 
     */
    public double variance()
    {
        double mu = mean();
        double variance = 0;

        double N = length();


        int used = 0;
        for(IndexValue x : this)
        {
            used++;
            variance += Math.pow(x.getValue()-mu, 2)/N;
        }
        //Now add all the zeros we skipped into it
        variance +=  (length()-used) * Math.pow(0-mu, 2)/N;
        
        return variance;
    }
    
    /**
     * Returns the median value in this vector