Example usage for org.apache.commons.math.analysis.integration UnivariateRealIntegrator setRelativeAccuracy

Introduction

In this page you can find the example usage for org.apache.commons.math.analysis.integration UnivariateRealIntegrator setRelativeAccuracy.

Prototype

void setRelativeAccuracy(double accuracy);

Source Link

Document

Set the relative accuracy.

Usage

From source file:sphericalGeo.SphericalDiffusionModel.java

/** anglerange[0] = lower bound, anglerange[1] = upper bound of range for angle2
 * **//*from   w  w w. j a  va  2 s.c  om*/
public double[] sample(double[] start, double time, double precision, double[] angleRange)
        throws ConvergenceException, FunctionEvaluationException, IllegalArgumentException {

    // first, sample an angle from the spherical diffusion density
    final double inverseVariance = precision / time;

    UnivariateRealFunction function = new UnivariateRealFunction() {
        @Override
        public double value(double x) throws FunctionEvaluationException {
            double logR = -x * x * inverseVariance / 2.0 + 0.5 * Math.log(x * Math.sin(x) * inverseVariance);

            return Math.exp(logR);
        }
    };

    UnivariateRealIntegrator integrator = new TrapezoidIntegrator();
    integrator.setAbsoluteAccuracy(1.0e-10);
    integrator.setRelativeAccuracy(1.0e-14);
    integrator.setMinimalIterationCount(2);
    integrator.setMaximalIterationCount(25);

    double[] cumulative = new double[NR_OF_STEPS];
    for (int i = 1; i < NR_OF_STEPS; i++) {
        cumulative[i] = cumulative[i - 1]
                + integrator.integrate(function, (i - 1) * Math.PI / NR_OF_STEPS, i * Math.PI / NR_OF_STEPS);
    }

    // normalise 
    double sum = cumulative[NR_OF_STEPS - 1];
    for (int i = 0; i < NR_OF_STEPS; i++) {
        cumulative[i] /= sum;
    }

    int i = Randomizer.randomChoice(cumulative);
    double angle = i * Math.PI / NR_OF_STEPS;

    // now we have an angle, use this to rotate the point [0,0] over
    // this angle in a random direction angle2
    double angle2 = angleRange[0] + Randomizer.nextDouble() * (angleRange[1] - angleRange[0]);
    //angleRange[0] = angle2;

    double[] xC = new double[] { Math.cos(angle), Math.sin(angle) * Math.cos(angle2),
            Math.sin(angle) * Math.sin(angle2) };

    // convert back to latitude, longitude relative to (lat=0, long=0)
    double[] xL = cartesian2Sperical(xC, true);
    //double [] sC = spherical2Cartesian(start[0], start[1]);
    double[] position = reverseMap(xL[0], xL[1], start[0], start[1]);
    return position;
}

---