smash::InterpolateDataSpline Class Reference

#include <interpolation.h>

Represent a cubic spline interpolation.

Definition at line 220 of file interpolation.h.

Collaboration diagram for smash::InterpolateDataSpline:

Public Member Functions
	InterpolateDataSpline (const std::vector< double > &x, const std::vector< double > &y)
	Interpolate function f given discrete samples f(x_i) = y_i. More...
	~InterpolateDataSpline ()
	Destructor. More...
double	operator() (double x) const
	Calculate spline interpolation at x. More...

Private Attributes
double	first_x_
	First x value. More...
double	last_x_
	Last x value. More...
double	first_y_
	First y value. More...
double	last_y_
	Last y value. More...
gsl_interp_accel *	acc_
	GSL iterator for interpolation lookups. More...
gsl_spline *	spline_
	GSL spline. More...

Constructor & Destructor Documentation

smash::InterpolateDataSpline::InterpolateDataSpline	(	const std::vector< double > &	x,
		const std::vector< double > &	y
	)

Interpolate function f given discrete samples f(x_i) = y_i.

Parameters

x	x-values.
y	y-values.

Returns

The interpolation function.

Cubic spline interpolation is used. Values outside the given samples will use the outmost sample as a constant extrapolation.

Definition at line 14 of file interpolation.cc.

                                                                         {
  const auto N = x.size();
  if (y.size() != N) {
    throw std::runtime_error(
        "Need two vectors of equal length for interpolation.");
  }
  if (N < 3) {
    throw std::runtime_error(
        "Need at least 3 data points for cubic spline interpolation.");
  }
  const auto p = generate_sort_permutation(
      x, [&](double const& a, double const& b) { return a < b; });
  const std::vector<double> sorted_x = apply_permutation(x, p);
  const std::vector<double> sorted_y = apply_permutation(y, p);
  check_duplicates(sorted_x, "InterpolateDataSpline");

  first_x_ = sorted_x.front();
  last_x_ = sorted_x.back();
  first_y_ = sorted_y.front();
  last_y_ = sorted_y.back();
  acc_ = gsl_interp_accel_alloc();
  spline_ = gsl_spline_alloc(gsl_interp_cspline, N);
  gsl_spline_init(spline_, &(*sorted_x.begin()), &(*sorted_y.begin()), N);
}

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smash::InterpolateDataSpline::~InterpolateDataSpline

(

)

Destructor.

Definition at line 40 of file interpolation.cc.

                                              {
  gsl_spline_free(spline_);
  gsl_interp_accel_free(acc_);
}

Member Function Documentation

double smash::InterpolateDataSpline::operator()

(

double

x

)

const

Calculate spline interpolation at x.

Parameters

x	Interpolation argument.

Returns

Interpolated value.

Definition at line 45 of file interpolation.cc.

                                                        {
  // constant extrapolation
  if (xi < first_x_) {
    return first_y_;
  }
  if (xi > last_x_) {
    return last_y_;
  }
  // cubic spline interpolation
  return gsl_spline_eval(spline_, xi, acc_);
}

Member Data Documentation

double smash::InterpolateDataSpline::first_x_

private

First x value.

Definition at line 249 of file interpolation.h.

double smash::InterpolateDataSpline::last_x_

private

Last x value.

Definition at line 251 of file interpolation.h.

double smash::InterpolateDataSpline::first_y_

private

First y value.

Definition at line 253 of file interpolation.h.

double smash::InterpolateDataSpline::last_y_

private

Last y value.

Definition at line 255 of file interpolation.h.

gsl_interp_accel* smash::InterpolateDataSpline::acc_

private

GSL iterator for interpolation lookups.

Definition at line 257 of file interpolation.h.

gsl_spline* smash::InterpolateDataSpline::spline_

private

GSL spline.

Definition at line 259 of file interpolation.h.

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The documentation for this class was generated from the following files:

• src/include/smash/interpolation.h
• src/interpolation.cc