CbmSplineFunction.h

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/*
 *====================================================================
 *
 *  Class for linear spline function used by CbmBilinearSpline class in CbmModels package
 *  
 *  Authors: V.Vovchenko
 *
 *  e-mail : 
 *
 *====================================================================
 *
 *  2D spline class
 *
 *====================================================================
 */
 
#ifndef SPLINEFUNCTION_H
#define SPLINEFUNCTION_H
#include <algorithm>
#include <cmath>
#include <vector>
 
class SplineFunction {
public:
  std::vector<std::pair<double, double>> vals;
  SplineFunction() : vals() { vals.resize(0); }
  SplineFunction(std::vector<double> x, std::vector<double> y) : vals() {
    for (unsigned int i = 0; i < x.size(); ++i) {
      vals.push_back(std::make_pair(x[i], y[i]));
    }
    sort(vals.begin(), vals.end());
  }
  void add_val(double x, double val) {
    vals.push_back(std::make_pair(x, val));
    sort(vals.begin(), vals.end());
  }
  double f(double arg) const {
    if (vals.size() < 2) return 0.;
    unsigned int ind             = 0;
    std::pair<double, double> op = std::make_pair(arg, 0.);
    std::vector<std::pair<double, double>>::const_iterator it =
      lower_bound(vals.begin(), vals.end(), op);
    ind = distance(vals.begin(), it);
    if (ind == 0)
      return vals[0].second
             + (arg - vals[0].first) * (vals[1].second - vals[0].second)
                 / (vals[1].first - vals[0].first);
    if (ind == vals.size())
      return vals[ind - 2].second
             + (arg - vals[ind - 2].first)
                 * (vals[ind - 1].second - vals[ind - 2].second)
                 / (vals[ind - 1].first - vals[ind - 2].first);
    return vals[ind - 1].second
           + (arg - vals[ind - 1].first)
               * (vals[ind].second - vals[ind - 1].second)
               / (vals[ind].first - vals[ind - 1].first);
  }
  double fsquare(double arg) {
    double ret = f(arg);
    return ret * ret;
  }
  void clear() {
    vals.resize(2);
    vals[0].first  = 0.;
    vals[0].second = 0.;
    vals[1].first  = 1.;
    vals[1].second = 0.;
  }
  void clearall() { vals.resize(0); }
  void fill(std::vector<double> x, std::vector<double> y) {
    vals.resize(0);
    for (unsigned int i = 0; i < x.size(); ++i) {
      vals.push_back(std::make_pair(x[i], y[i]));
    }
    sort(vals.begin(), vals.end());
  }
  void setConstant(double val) {
    vals.resize(0);
    vals.push_back(std::make_pair(0., val));
    vals.push_back(std::make_pair(1., val));
  }
};
 
 
#endif  // SPLINEFUNCTION_H