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/*
 * JGrass - Free Open Source Java GIS http://www.jgrass.org 
 * (C) HydroloGIS - www.hydrologis.com 
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Library General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option) any
 * later version.
 * 
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Library General Public License
 * along with this library; if not, write to the Free Foundation, Inc., 59
 * Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package org.jgrasstools.gears.utils.math.integration;

import org.jgrasstools.gears.libs.modules.ModelsEngine;

/**
 * @author Andrea Antonello (www.hydrologis.com)
 */
public class ConvolutionDiffusionWidth extends SimpsonIntegral implements IntegrableFunction {

    private double[][] ampi_diffusion = null;

    private double D = 0f;

    private double t = 0;

    /**
     * Calculates the integral of the diffusion equation
     * 
     * @param lowerintegrationlimit - the lower limit of integration
     * @param upperintegrationlimit - the upper limit of integration
     * @param maximalsteps- maximal number of bins in which to divide the interval
     * @param integrationaccuracy - value of accuracy of integration
     * @param ampiFunction
     * @param diffusionparam
     * @param time
     * @param integrationtype
     */
    public ConvolutionDiffusionWidth( double lowerintegrationlimit, double upperintegrationlimit, int maximalsteps,
            double integrationaccuracy, double[][] ampiFunction, double diffusionparam, double time ) {
        lowerlimit = lowerintegrationlimit;
        upperlimit = upperintegrationlimit;
        maxsteps = maximalsteps;
        accuracy = integrationaccuracy;
        strapezoid = 0f;
        ampi_diffusion = ampiFunction;
        D = diffusionparam;
        t = time;
    }

    public void updateTime( int newt ) {
        t = newt;
    }

    public double integrate() {
        return simpson();
    }

    protected double equation( double x ) {
        double result = x > ampi_diffusion[ampi_diffusion.length - 1][0] ? 0.0 : 1
                / Math.sqrt(4 * Math.PI * D * Math.pow(t, 3.0f)) * ModelsEngine.width_interpolate(ampi_diffusion, x, 0, 1) * x
                / (Math.exp(Math.pow((x - t), 2) / (4 * D * t)));

        return result;
    }

}