Spline.h

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#if !defined(LSST_AFW_MATH_DETAIL_SPLINE)
#define LSST_AFW_MATH_DETAIL_SPLINE 1
#include <cmath>
#include <vector>
 
namespace lsst {
namespace afw {
namespace math {
namespace detail {
 
/*
 * Splines
 */
class Spline {
public:
    virtual ~Spline() = default;
 
    Spline(Spline const&) = default;
    Spline(Spline&&) = default;
    Spline& operator=(Spline const&) = default;
    Spline& operator=(Spline&&) = default;

    void interpolate(std::vector<double> const& x, std::vector<double>& y) const;
    void derivative(std::vector<double> const& x, std::vector<double>& dydx) const;

    std::vector<double> roots(double const value, double const x0, double const x1) const;
 
protected:
    Spline() = default;
    void _allocateSpline(int const nknot);
 
    std::vector<double> _knots;                 // positions of knots
    std::vector<std::vector<double> > _coeffs;  // and associated coefficients
};
 
class TautSpline : public Spline {
public:
    enum Symmetry { Unknown, Odd, Even };

    TautSpline(std::vector<double> const& x, std::vector<double> const& y, double const gamma = 0,
               Symmetry type = Unknown);
 
private:
    void calculateTautSpline(std::vector<double> const& x, std::vector<double> const& y, double const gamma0);
    void calculateTautSplineEvenOdd(std::vector<double> const& x, std::vector<double> const& y,
                                    double const gamma0, bool even);
};
 
class SmoothedSpline : public Spline {
public:
    SmoothedSpline(std::vector<double> const& x, std::vector<double> const& y, std::vector<double> const& dy,
                   double s, double* chisq = nullptr, std::vector<double>* errs = nullptr);
};
}  // namespace detail
}  // namespace math
}  // namespace afw
}  // namespace lsst
#endif