smash::InterpolateData2DSpline Class Reference

#include <interpolation2D.h>

Represent a bicubic spline interpolation.

Definition at line 20 of file interpolation2D.h.

Public Member Functions
	InterpolateData2DSpline (const std::vector< double > &x, const std::vector< double > &y, const std::vector< double > &z)
	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
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 *	xacc_
	GSL iterator for interpolation lookups in x direction. More...
gsl_interp_accel *	yacc_
	GSL iterator for interpolation lookupin y direction. More...
gsl_spline2d *	spline_
	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
	)

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

Parameters

x	x-values.
y	y-values.
z	z-values

Returns

The interpolation function.

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

Definition at line 16 of file interpolation2D.cc.

                                                                             {
  const size_t M = x.size();
  const size_t N = y.size();
 
  if (z.size() != N * M) {
    throw std::runtime_error(
        "Dimensions not suitable for 2D interpolation. DIM(z) != DIM(x) * "
        "DIM(y).");
  }
 
  if (M < 4 || N < 4) {
    throw std::runtime_error(
        "Need at least 4 data points in each dimension for bicubic spline "
        "interpolation.");
  }
 
  // 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 54 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.

Definition at line 60 of file interpolation2D.cc.

                                                                     {
  // 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

first_x_

double smash::InterpolateData2DSpline::first_x_

private

First x value.

Definition at line 52 of file interpolation2D.h.

last_x_

double smash::InterpolateData2DSpline::last_x_

private

Last x value.

Definition at line 54 of file interpolation2D.h.

first_y_

double smash::InterpolateData2DSpline::first_y_

private

First y value.

Definition at line 56 of file interpolation2D.h.

last_y_

double smash::InterpolateData2DSpline::last_y_

private

Last y value.

Definition at line 58 of file interpolation2D.h.

xacc_

gsl_interp_accel* smash::InterpolateData2DSpline::xacc_

private

GSL iterator for interpolation lookups in x direction.

Definition at line 61 of file interpolation2D.h.

yacc_

gsl_interp_accel* smash::InterpolateData2DSpline::yacc_

private

GSL iterator for interpolation lookupin y direction.

Definition at line 63 of file interpolation2D.h.

spline_

gsl_spline2d* smash::InterpolateData2DSpline::spline_

private

GSL spline in 2D.

Definition at line 65 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