numerics.cpp
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/***************************************************************************
* numerics.cpp - Illustrates numerical class usage *
* ----------------------------------------------------------------------- *
* copyright (C) 2013-2014 by Juergen Knoedlseder *
* ----------------------------------------------------------------------- *
* *
* This program 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. *
* *
* This program 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 this program. If not, see <http://www.gnu.org/licenses/>. *
* *
***************************************************************************/
/**
* @file numerics.cpp
* @brief Illustrates numerical class usage
* @author Juergen Knoedlseder
*/
/* __ Includes ___________________________________________________________ */
#include "GammaLib.hpp"
/***********************************************************************//**
* @brief Gaussian function
*
* This code illustrates the definition of a Gaussian function.
***************************************************************************/
class function : public GFunction {
public:
function(const double& sigma) : m_a(1.0/(sigma*std::sqrt(gammalib::twopi))),
m_sigma(sigma) {}
double eval(const double& x) { return m_a*std::exp(-0.5*x*x/(m_sigma*m_sigma)); }
protected:
double m_a; //!< Amplitude parameter
double m_sigma; //!< Width parameter
};
/***********************************************************************//**
* @brief Integrate function
*
* This code illustrates the integration of a function.
***************************************************************************/
int main(void) {
// Create instance of function
function fct(3.0);
// Create an integral object based on the function
GIntegral integral(&fct);
// Set relative integration precision
integral.eps(1.0e-8);
// Integrate over the interval [-10,10]
double result = integral.romberg(-15.0, +15.0);
// Print result (should be basically 1)
std::cout << "Integral: " << result << std::endl;
// Create a derivative object based on the function
GDerivative derivative(&fct);
// Print derivatives
std::cout << "Derivative(0): " << derivative.value(0.0) << std::endl;
std::cout << "Derivative(3): " << derivative.value(3.0) << std::endl;
std::cout << "Derivative(-3): " << derivative.value(-3.0) << std::endl;
// Exit
return 0;
}