smash::InterpolateData2DSpline Class Reference

#include <interpolation2D.h>

Represent a bicubic spline interpolation.

Definition at line 23 of file interpolation2D.h.

Collaboration diagram for smash::InterpolateData2DSpline:

Public Member Functions
	InterpolateData2DSpline (const std::vector< double > &x, const std::vector< double > &y, const std::vector< double > &z, ExtrapolationType extrapolation_type=ExtrapolationType::None)
	Interpolate function f given discrete samples f(x_i, y_i) = z_i. More...
	~InterpolateData2DSpline ()
	Destructor. More...
double	operator() (double xi, double yi) const
	Calculate bicubic interpolation for given x and y. 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 *	xacc_ = nullptr
	GSL iterator for interpolation lookups in x direction. More...
gsl_interp_accel *	yacc_ = nullptr
	GSL iterator for interpolation lookupin y direction. More...
gsl_spline2d *	spline_ = nullptr
	GSL spline in 2D. More...

Constructor & Destructor Documentation

InterpolateData2DSpline()

smash::InterpolateData2DSpline::InterpolateData2DSpline	(	const std::vector< double > &	x,
		const std::vector< double > &	y,
		const std::vector< double > &	z,
		ExtrapolationType	extrapolation_type = ExtrapolationType::None
	)

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

A bicubic spline interpolation is used.

Parameters

x	x-values.
y	y-values.
z	z-values
extrapolation_type	Type of extrapolation for requested x_i and y_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::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.
std::invalid_argument	if product of dimensions of x and y does not equal dimension of z.
std::invalid_argument	if less than three data points in x or y are provided.
std::invalid_argument	if x and y are not sorted that their values strictly increase.

Definition at line 18 of file interpolation2D.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 size_t M = x.size();
  const size_t N = y.size();
 
  if (z.size() != N * M) {
    throw std::invalid_argument(
        "Dimensions not suitable for 2D interpolation. DIM(z) != DIM(x) * "
        "DIM(y).");
  }
 
  if (M < 4 || N < 4) {
    throw std::invalid_argument(
        "Need at least 4 data points in each dimension for bicubic spline "
        "interpolation.");
  }
 
  if (!std::is_sorted(x.begin(), x.end()) ||
      !std::is_sorted(y.begin(), y.end())) {
    throw std::invalid_argument(
        "x and y values must be strictly increasing, i.e. the vectors have to "
        "be sorted by size of their values. This is required by GSL.");
  }
 
  // Assign lower and upper bounds for constant extrapolation
  first_x_ = x.front();
  last_x_ = x.back();
  first_y_ = y.front();
  last_y_ = y.back();
 
  // cast vectors into arrays, as GSL functions can only handle arrays
  const double* xa = &x[0];
  const double* ya = &y[0];
  const double* za = &z[0];
 
  // Create accelerator objects (interpolation lookups)
  xacc_ = gsl_interp_accel_alloc();
  yacc_ = gsl_interp_accel_alloc();
 
  // Initialize bicubic spline interpolation
  spline_ = gsl_spline2d_alloc(gsl_interp2d_bicubic, M, N);
  gsl_spline2d_init(spline_, xa, ya, za, M, N);
}

~InterpolateData2DSpline()

smash::InterpolateData2DSpline::~InterpolateData2DSpline

(

)

Destructor.

Definition at line 75 of file interpolation2D.cc.

                                                  {
  gsl_spline2d_free(spline_);
  gsl_interp_accel_free(xacc_);
  gsl_interp_accel_free(yacc_);
}

Member Function Documentation

operator()()

double smash::InterpolateData2DSpline::operator()	(	double	xi,
		double	yi
	)		const

Calculate bicubic interpolation for given x and y.

Parameters

xi	Interpolation argument in first dimension.
yi	Interpolation argument in second dimension.

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 81 of file interpolation2D.cc.

                                                                     {
  if ((xi < first_x_ || xi > last_x_) || (yi < first_y_ || yi > last_y_)) {
    if (extrapolation_type_ == ExtrapolationType::None) {
      std::ostringstream error_msg{
          "InterpolateData2DSpline only accepts x and y values within the "
          "range of the underlying data\nwhen extrapolation is not specified. ",
          std::ios::ate};
      error_msg << "x value " << xi << " or y value " << yi
                << " are 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) {
      // constant extrapolation at the edges
      xi = (xi < first_x_) ? first_x_ : xi;
      xi = (xi > last_x_) ? last_x_ : xi;
      yi = (yi < first_y_) ? first_y_ : yi;
      yi = (yi > last_y_) ? last_y_ : yi;
    }
  }
 
  // bicubic spline interpolation
  return gsl_spline2d_eval(spline_, xi, yi, xacc_, yacc_);
}

Member Data Documentation

extrapolation_type_

ExtrapolationType smash::InterpolateData2DSpline::extrapolation_type_ = ExtrapolationType::None

private

Extrapolation type.

Definition at line 75 of file interpolation2D.h.

first_x_

double smash::InterpolateData2DSpline::first_x_ = smash_NaN<double>

private

First x value of underlying data.

Definition at line 77 of file interpolation2D.h.

last_x_

double smash::InterpolateData2DSpline::last_x_ = smash_NaN<double>

private

Last x value of underlying data.

Definition at line 79 of file interpolation2D.h.

first_y_

double smash::InterpolateData2DSpline::first_y_ = smash_NaN<double>

private

First y value of underlying data.

Definition at line 81 of file interpolation2D.h.

last_y_

double smash::InterpolateData2DSpline::last_y_ = smash_NaN<double>

private

Last y value of underlying data.

Definition at line 83 of file interpolation2D.h.

xacc_

gsl_interp_accel* smash::InterpolateData2DSpline::xacc_ = nullptr

private

GSL iterator for interpolation lookups in x direction.

Definition at line 86 of file interpolation2D.h.

yacc_

gsl_interp_accel* smash::InterpolateData2DSpline::yacc_ = nullptr

private

GSL iterator for interpolation lookupin y direction.

Definition at line 88 of file interpolation2D.h.

spline_

gsl_spline2d* smash::InterpolateData2DSpline::spline_ = nullptr

private

GSL spline in 2D.

Definition at line 90 of file interpolation2D.h.

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

• src/include/smash/interpolation2D.h
• src/interpolation2D.cc