com.gedaeusp.domain.BiexponentialParametric.java Source code

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Here is the source code for com.gedaeusp.domain.BiexponentialParametric.java

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/*
Copyright 2014 Antnio Miranda, Caio Valente, Igor Topcin, Jorge Melegati, Thales Paiva, Victor Santos
    
This file is part of PhysUSP.
    
PhysUSP is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
    
PhysUSP 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 General Public License for more details.
    
You should have received a copy of the GNU General Public License
along with PhysUSP. If not, see <http://www.gnu.org/licenses/>.
*/

package com.gedaeusp.domain;

import org.apache.commons.math3.analysis.ParametricUnivariateFunction;
import org.apache.commons.math3.util.FastMath;

import com.gedaeusp.domain.Biexponential;

public class BiexponentialParametric implements ParametricUnivariateFunction {

    private boolean fixedV0;

    public BiexponentialParametric() {
        this(false);
    }

    public BiexponentialParametric(boolean fixedV0) {
        this.fixedV0 = fixedV0;
    }

    @Override
    public double value(double t, double... params) {
        double v0 = params[Biexponential.PARAM_v0];
        double a1 = params[Biexponential.PARAM_a1];
        double a2 = params[Biexponential.PARAM_a2];
        double tau1 = params[Biexponential.PARAM_tau1];
        double tau2 = params[Biexponential.PARAM_tau2];

        return Biexponential.value(t, v0, a1, a2, tau1, tau2);
    }

    @Override
    public double[] gradient(double t, double... params) {
        double a1 = params[Biexponential.PARAM_a1];
        double a2 = params[Biexponential.PARAM_a2];
        double tau1 = params[Biexponential.PARAM_tau1];
        double tau2 = params[Biexponential.PARAM_tau2];

        double dv0 = fixedV0 == true ? 0 : 1;
        double da1 = FastMath.exp(-t / tau1);
        double da2 = FastMath.exp(-t / tau2);
        double dTau1 = (a1 * t * FastMath.exp(-t / tau1)) / FastMath.pow(tau1, 2);
        double dTau2 = (a2 * t * FastMath.exp(-t / tau2)) / FastMath.pow(tau2, 2);

        return new double[] { dv0, da1, da2, dTau1, dTau2 };
    }

}