smash::InterpolateDataSpline Class Reference

#include <interpolation.h>

Represent a cubic spline interpolation.

Definition at line 272 of file interpolation.h.

Collaboration diagram for smash::InterpolateDataSpline:

Public Member Functions
	InterpolateDataSpline (const std::vector< double > &x, const std::vector< double > &y, ExtrapolationType extrapolation_type=ExtrapolationType::None)
	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
ExtrapolationType	extrapolation_type_ = ExtrapolationType::None
	Extrapolation type. More...
double	first_x_ = smash_NaN<double>
	First x value of underlying data. More...
double	last_x_ = smash_NaN<double>
	Last x value of underlying data. More...
double	first_y_ = smash_NaN<double>
	First y value of underlying data. More...
double	last_y_ = smash_NaN<double>
	Last y value of underlying data. More...
gsl_interp_accel *	acc_ = nullptr
	GSL iterator for interpolation lookups. More...
gsl_spline *	spline_ = nullptr
	GSL spline. More...

Constructor & Destructor Documentation

InterpolateDataSpline()

smash::InterpolateDataSpline::InterpolateDataSpline	(	const std::vector< double > &	x,
		const std::vector< double > &	y,
		ExtrapolationType	extrapolation_type = ExtrapolationType::None
	)

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

Cubic spline interpolation is used.

Parameters

x	x-values.
y	y-values.
extrapolation_type	Type of extrapolation for requested x_i values that are out of bounds. Extrapolation is by default disabled. Possible types are None, Zero, and Constant.

Returns

The interpolation function.

Exceptions

std::invalid_argument	if vectors x and y have different length.
std::invalid_argument	if less than 3 data points are provided.
std::out_of_range	if values outside of the boundaries of the underlying data are tried to be accessed and extrapolation is disabled.
std::invalid_argument	if unsupported extrapolation type is requested.

Definition at line 14 of file interpolation.cc.

    : extrapolation_type_{extrapolation_type} {
  switch (extrapolation_type_) {
    case ExtrapolationType::None:
    case ExtrapolationType::Zero:
    case ExtrapolationType::Constant:
      break;
    default:
      throw std::invalid_argument(
          "The provided extrapolation type is not supported. Valid types are "
          "'None', 'Zero', and 'Constant'.");
  }
  const auto N = x.size();
  if (y.size() != N) {
    throw std::invalid_argument(
        "The interpolation requires two vectors of equal length.");
  }
  if (N < 3) {
    throw std::invalid_argument(
        "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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~InterpolateDataSpline()

smash::InterpolateDataSpline::~InterpolateDataSpline

(

)

Destructor.

Definition at line 52 of file interpolation.cc.

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

Member Function Documentation

operator()()

double smash::InterpolateDataSpline::operator()

(

double

x

)

const

Calculate spline interpolation at x.

Parameters

x	Interpolation argument.

Returns

Interpolated value.

Exceptions

std::out_of_range

if values outside of the boundaries of the underlying data are tried to be accessed and extrapolation is disabled.

Definition at line 57 of file interpolation.cc.

                                                        {
  if (xi < first_x_ || xi > last_x_) {
    if (extrapolation_type_ == ExtrapolationType::None) {
      std::ostringstream error_msg{
          "InterpolateDataSpline only accepts x values within the range of the "
          "underlying data\nwhen an extrapolation type is not specified. ",
          std::ios::ate};
      error_msg << "x value " << xi << " is out of bounds.";
      throw std::out_of_range(error_msg.str());
    } else if (extrapolation_type_ == ExtrapolationType::Zero) {
      return 0.;
    } else if (extrapolation_type_ == ExtrapolationType::Constant) {
      return (xi < first_x_) ? first_y_ : last_y_;
    }
  }
  // cubic spline interpolation
  return gsl_spline_eval(spline_, xi, acc_);
}

Member Data Documentation

extrapolation_type_

ExtrapolationType smash::InterpolateDataSpline::extrapolation_type_ = ExtrapolationType::None

private

Extrapolation type.

Definition at line 316 of file interpolation.h.

first_x_

double smash::InterpolateDataSpline::first_x_ = smash_NaN<double>

private

First x value of underlying data.

Definition at line 318 of file interpolation.h.

last_x_

double smash::InterpolateDataSpline::last_x_ = smash_NaN<double>

private

Last x value of underlying data.

Definition at line 320 of file interpolation.h.

first_y_

double smash::InterpolateDataSpline::first_y_ = smash_NaN<double>

private

First y value of underlying data.

Definition at line 322 of file interpolation.h.

last_y_

double smash::InterpolateDataSpline::last_y_ = smash_NaN<double>

private

Last y value of underlying data.

Definition at line 324 of file interpolation.h.

acc_

gsl_interp_accel* smash::InterpolateDataSpline::acc_ = nullptr

private

GSL iterator for interpolation lookups.

Definition at line 326 of file interpolation.h.

spline_

gsl_spline* smash::InterpolateDataSpline::spline_ = nullptr

private

GSL spline.

Definition at line 328 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