package com.imsl.test.example.stat.distributions;

import com.imsl.math.PrintMatrix;
import com.imsl.math.PrintMatrixFormat;
import com.imsl.stat.distributions.WeibullPD;
import java.text.DecimalFormat;

/**
 * <p>
 * Evaluates the Weibull probability distribution.</p>
 * <p>
 * This example evaluates the Weibull density, gradient, and hessian for a small
 * sample of data.</p>
 *
 * @see <a href="WeibullPDEx1.java">Code</a>
 * @see <a href="doc-files/WeibullPDEx1.out">Output</a>
 */
public class WeibullPDEx1 {

    public static void main(String[] args) {

        double[] x = {0, .5, 1, 4, 9};
        WeibullPD wpd = new WeibullPD();

        double[] values = new double[x.length];
        for (int i = 0; i < x.length; i++) {
            values[i] = wpd.pdf(x[i], 3.0, 2.0);
        }
        
        PrintMatrixFormat pmf = new PrintMatrixFormat();
        pmf.setNumberFormat(new DecimalFormat("0.000000000"));

        PrintMatrix pm = new PrintMatrix("Weibull(3.0,2.0) pdf values at x=");
        pm.print(pmf, x);

        pm.setTitle("f(x;3.0,2.0)=");
        pm.print(pmf, values);

        double[] gradient = wpd.getPDFGradientApproximation(x[2], 3.0, 2.0);
        
        String title = String.format("Approximate gradient of f(x;3.0,2.0) at x= %1.8f",x[2]);
        pm.setTitle(title);
        pm.print(pmf, gradient);
        
        gradient = wpd.getPDFGradient(x[2], 3.0, 2.0);
        
        title = String.format("Analytic gradient of f(x;3.0,2.0) at x= %1.8f",x[2]);
        pm.setTitle(title);
        pm.print(pmf, gradient);
        
        double[][] hessian = wpd.getPDFHessianApproximation(x[2], 3.0, 2.0);
        
        title = String.format("Approximate Hessian of f(x;3.0,2.0) at x= %1.8f",x[2]);
        pm.setTitle(title);
        pm.print(pmf, hessian);
        
        hessian = wpd.getPDFHessian(x[2], 3.0, 2.0);
        
        title = String.format("Analytic Hessian of f(x;3.0,2.0) at x= %1.8f",x[2]);
        pm.setTitle(title);
        pm.print(pmf, hessian);
    }
}