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Chebyshev.h
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Chebyshev.h
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// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2007 ISIS Rutherford Appleton Laboratory UKRI,
// NScD Oak Ridge National Laboratory, European Spallation Source,
// Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#pragma once
//----------------------------------------------------------------------
// Includes
//----------------------------------------------------------------------
#include "MantidCurveFitting/Functions/BackgroundFunction.h"
#include <valarray>
namespace Mantid {
namespace CurveFitting {
namespace Functions {
/**
Implements Chebyshev polynomial expansion.
Attributes: int n - the highest polynomial order.
Parameters: n+1 expansion coefficients \f$a_i\f$ as in expression:
\f$\sum_{i=0}^{n} a_i T_i(x)\f$
Uses the Clenshaw algorithm to evaluate the expansion.
@author Roman Tolchenov, Tessella inc
@date 14/05/2010
*/
class MANTID_CURVEFITTING_DLL Chebyshev : public BackgroundFunction {
public:
/// Constructor
Chebyshev();
/// overwrite IFunction base class methods
std::string name() const override { return "Chebyshev"; }
const std::string category() const override { return "Background"; }
void function1D(double *out, const double *xValues, const size_t nData) const override;
void functionDeriv1D(API::Jacobian *out, const double *xValues, const size_t nData) override;
/// Set a value to attribute attName
void setAttribute(const std::string &attName, const Attribute &) override;
private:
/// Polynomial order
int m_n;
/// Lower x boundary. The default is -1
double m_StartX;
/// Upper x boundary. The default is 1
double m_EndX;
/// Keep intermediate calculatons
mutable std::valarray<double> m_b;
};
using Chebyshev_sptr = std::shared_ptr<Chebyshev>;
} // namespace Functions
} // namespace CurveFitting
} // namespace Mantid