Detailed Description

This header covers the routines for interpolation.

Synopsis

#include <lal/Interpolate.h>

Description

The routine LALSPolynomialInterpolation() computes the interpolated \(y\) value output at the \(x\) value target by fitting a polynomial of order params.n-1 to the data. The result output is of type SInterpolateOut, which contains the value output.y as well as an estimate of the error output.dy. The routine LALDPolynomialInterpolation() is the same but for double precision.

Operating Instructions

The following program fits a fourth-order polynomial to the five data points \(\{(0,0),(1,1),(2,3),(3,4),(4,3)\}\), and interpolates the value at \(x=2.4\).

#include <lal/LALStdlib.h>
#include <lal/Interpolate.h>
 
int main ()
{
enum { ArraySize = 5 };
static LALStatus status;
REAL4            x[ArraySize] = {0,1,2,3,4};
REAL4            y[ArraySize] = {0,1,3,4,3};
REAL4            target       = 2.4;
SInterpolatePar  intpar       = {ArraySize, x, y};
SInterpolateOut  intout;
 
LALSPolynomialInterpolation( &status, &intout, target, &intpar );
 
return 0;
}

Algorithm

This is an implementation of the Neville algroithm, see polint in Numerical Recipes [22] .

Prototypes
void	LALSPolynomialInterpolation (LALStatus status, SInterpolateOut output, REAL4 target, SInterpolatePar *params)

void	LALDPolynomialInterpolation (LALStatus status, DInterpolateOut output, REAL8 target, DInterpolatePar *params)

REAL8	XLALREAL8PolynomialInterpolation (REAL8 yout, REAL8 xtarget, REAL8 y, REAL8 *x, UINT4 n)

int	XLALREAL8Interpolation (REAL8Sequence x_in, REAL8Sequence y_in, REAL8Sequence x_out, REAL8Sequence y_out, UINT4 n_data_points, const gsl_interp_type *itrp_type)

int	XLALREAL8TimeSeriesInterpolation (REAL8TimeSeries ts_in, REAL8Sequence y_in, REAL8Sequence t_in, REAL8Sequence t_out, UINT4 n_data_points, const gsl_interp_type *itrp_type)

Data Structures
struct	SInterpolateOut
	These structures contain the output of the interpolation. More...

struct	DInterpolateOut
	These structures contain the output of the interpolation. More...

struct	SInterpolatePar
	These structures contain the interpolation parameters; These are the arrays of `n` domain values \(x[0] \ldots x[n-1]\) and their corresponding values \(y[0] \ldots y[n-1]\). More...

struct	DInterpolatePar
	These structures contain the interpolation parameters; These are the arrays of `n` domain values \(x[0]\ldots x[n-1]\) and their corresponding values \(y[0]\ldots y[n-1]\). More...

Files
file	InterpolateTest.c
	Tests the routines in Interpolate.h.

Error Codes
#define	INTERPOLATEH_ENULL 1
	Null pointer. More...

#define	INTERPOLATEH_ESIZE 2
	Invalid size. More...

#define	INTERPOLATEH_EZERO 4
	Zero divide. More...

Function Documentation

◆ LALSPolynomialInterpolation()

void LALSPolynomialInterpolation	(	LALStatus *	status,
		SInterpolateOut *	output,
		REAL4	target,
		SInterpolatePar *	params
	)

See also: See Header Interpolate.h for documentation

Definition at line 29 of file Interpolate.c.

◆ LALDPolynomialInterpolation()

void LALDPolynomialInterpolation	(	LALStatus *	status,
		DInterpolateOut *	output,
		REAL8	target,
		DInterpolatePar *	params
	)

See also: See Header Interpolate.h for documentation

Definition at line 115 of file Interpolate.c.

◆ XLALREAL8PolynomialInterpolation()

REAL8 XLALREAL8PolynomialInterpolation	(	REAL8 *	yout,
		REAL8	xtarget,
		REAL8 *	y,
		REAL8 *	x,
		UINT4	n
	)

See also: See Header Interpolate.h for documentation

Definition at line 140 of file Interpolate.c.

◆ XLALREAL8Interpolation()

int XLALREAL8Interpolation	(	REAL8Sequence *	x_in,
		REAL8Sequence *	y_in,
		REAL8Sequence *	x_out,
		REAL8Sequence *	y_out,
		UINT4	n_data_points,
		const gsl_interp_type *	itrp_type
	)

Definition at line 228 of file Interpolate.c.

◆ XLALREAL8TimeSeriesInterpolation()

int XLALREAL8TimeSeriesInterpolation	(	REAL8TimeSeries *	ts_in,
		REAL8Sequence *	y_in,
		REAL8Sequence *	t_in,
		REAL8Sequence *	t_out,
		UINT4	n_data_points,
		const gsl_interp_type *	itrp_type
	)

Definition at line 282 of file Interpolate.c.

Macro Definition Documentation

◆ INTERPOLATEH_ENULL

#define INTERPOLATEH_ENULL 1

Null pointer.

Definition at line 91 of file Interpolate.h.

◆ INTERPOLATEH_ESIZE

#define INTERPOLATEH_ESIZE 2

Invalid size.

Definition at line 92 of file Interpolate.h.

◆ INTERPOLATEH_EZERO

#define INTERPOLATEH_EZERO 4

Zero divide.

Definition at line 93 of file Interpolate.h.