spline.h

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/*
 * Copyright 2010-2020 The VOTCA Development Team (http://www.votca.org)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
 
#ifndef VOTCA_TOOLS_SPLINE_H
#define VOTCA_TOOLS_SPLINE_H
 
// Local VOTCA includes
#include "eigen.h"
#include "types.h"
 
namespace votca {
namespace tools {

 
class Spline {
 public:
  Spline() = default;
 
  virtual ~Spline() = default;

  virtual void Interpolate(const Eigen::VectorXd &x,
                           const Eigen::VectorXd &y) = 0;

  virtual void Fit(const Eigen::VectorXd &x, const Eigen::VectorXd &y) = 0;

  virtual double Calculate(double x) = 0;

  virtual double CalculateDerivative(double x) = 0;

  enum eBoundary {
    splineNormal = 0,         
    splinePeriodic = 1,       
    splineDerivativeZero = 2  
  };

  void setBC(eBoundary bc) { boundaries_ = bc; }

  void setBCInt(Index bc) {
    switch (bc) {
      case 0:
        boundaries_ = splineNormal;
        break;
      case 1:
        boundaries_ = splinePeriodic;
        break;
      case 2:
        boundaries_ = splineDerivativeZero;
        break;
    }
  }

  double getGridPoint(int i);

  Eigen::VectorXd Calculate(const Eigen::VectorXd &x);

  Eigen::VectorXd CalculateDerivative(const Eigen::VectorXd &x);

  void Print(std::ostream &out, double interval);

  Index getInterval(double r);

  Index GenerateGrid(double min, double max, double h);

  Eigen::VectorXd &getX() { return r_; }
  const Eigen::VectorXd &getX() const { return r_; }
  // Eigen::VectorXd &getSplineF() { return  f_; }
  // const Eigen::VectorXd &getSplineF() const { return  f_; }

  // Eigen::VectorXd &getSplineF2() { return  f2_; }
  // const Eigen::VectorXd &getSplineF2() const { return  f_; }
 
 protected:
  eBoundary boundaries_ = eBoundary::splineNormal;
  // the grid points
  Eigen::VectorXd r_;
};
 
}  // namespace tools
}  // namespace votca
 
#endif  // VOTCA_TOOLS_SPLINE_H