Class PowVariogram

JSAT/src/jsat/regression/OrdinaryKriging.java:327–379

    }
    
    public static class PowVariogram implements Variogram
    {
        private double alpha;
        private double beta;

        public PowVariogram()
        {
            this(1.5);
        }

        public PowVariogram(double beta)
        {
            this.beta = beta;
        }

        @Override
        public void train(RegressionDataSet dataSet, double nugget)
        {
            int npt=dataSet.getSampleSize();
            double num=0,denom=0, nugSqrd = nugget*nugget;

            for (int i = 0; i < npt; i++)
            {
                Vec xi = dataSet.getDataPoint(i).getNumericalValues();
                double yi = dataSet.getTargetValue(i);
                for (int j = i + 1; j < npt; j++)
                {
                    Vec xj = dataSet.getDataPoint(j).getNumericalValues();
                    double yj = dataSet.getTargetValue(j);
                    double rb = pow(xi.pNormDist(2, xj), beta);
                    
                    num += rb* (0.5* pow(yi-yj, 2)-nugSqrd);
                    denom += rb*rb;
                }
            }
            alpha = num / denom;
        }
        
        @Override
        public double val(double r)
        {
            return alpha*pow(r, beta);
        }

        @Override
        public Variogram clone()
        {
            PowVariogram clone = new PowVariogram(beta);
            clone.alpha = this.alpha;
            
            return clone;
        }
    }
    
}