QwtSpline Class Reference

List of all members.

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Detailed Description

A class for spline interpolation.

The QwtSpline class is used for cubical spline interpolation. Two types of splines, natural and periodic, are supported.

Usage:

1. First call setPoints() to determine the spline coefficients for a tabulated function y(x).
2. After the coefficients have been set up, the interpolated function value for an argument x can be determined by calling QwtSpline::value().

Example:

#include <qwt_spline.h>

QPolygonF interpolate(const QPolygonF& points, int numValues)
{
    QwtSpline spline;
    if ( !spline.setPoints(points) ) 
        return points;

    QPolygonF interpolatedPoints(numValues);

    const double delta = 
        (points[numPoints - 1].x() - points[0].x()) / (points.size() - 1);
    for(i = 0; i < points.size(); i++)  / interpolate
    {
        const double x = points[0].x() + i * delta;
        interpolatedPoints[i].setX(x);
        interpolatedPoints[i].setY(spline.value(x));
    }
    return interpolatedPoints;
}

Definition at line 77 of file qwt_spline.h.

Public Types
enum	SplineType {   Natural,   Periodic }
Public Member Functions
	QwtSpline ()
	QwtSpline (const QwtSpline &)
	~QwtSpline ()
QwtSpline &	operator= (const QwtSpline &)
void	setSplineType (SplineType)
SplineType	splineType () const
bool	setPoints (const QPolygonF &points)
QPolygonF	points () const
void	reset ()
bool	isValid () const
double	value (double x) const
Protected Member Functions
bool	buildNaturalSpline (const QPolygonF &)
bool	buildPeriodicSpline (const QPolygonF &)
Protected Attributes
PrivateData *	d_data

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Constructor & Destructor Documentation

QwtSpline::QwtSpline (   )

Constructor. Definition at line 73 of file qwt_spline.cpp. References d_data.

QwtSpline::~QwtSpline (   )

Destructor. Definition at line 90 of file qwt_spline.cpp. References d_data.

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Member Function Documentation

bool QwtSpline::buildNaturalSpline (  const QPolygonF &  points  )  [protected]

Determines the coefficients for a natural spline. Returns: true if successful Definition at line 209 of file qwt_spline.cpp.

bool QwtSpline::buildPeriodicSpline (  const QPolygonF &  points  )  [protected]

Determines the coefficients for a periodic spline. Returns: true if successful Definition at line 292 of file qwt_spline.cpp.

bool QwtSpline::isValid (   )  const

True if valid. Definition at line 181 of file qwt_spline.cpp. References d_data.

QPolygonF QwtSpline::points (   )  const

Return points passed by setPoints Definition at line 164 of file qwt_spline.cpp.

void QwtSpline::reset (   )

Free allocated memory and set size to 0. Definition at line 172 of file qwt_spline.cpp. References d_data.

bool QwtSpline::setPoints (  const QPolygonF &  points  )

Determine the function table index corresponding to a value x Calculate the spline coefficients. Depending on the value of periodic, this function will determine the coefficients for a natural or a periodic spline and store them internally. Parameters: x  y  points size  number of points periodic  if true, calculate periodic spline Returns: true if successful Warning: The sequence of x (but not y) values has to be strictly monotone increasing, which means x[0] < x[1] < .... < x[n-1]. If this is not the case, the function will return false Definition at line 126 of file qwt_spline.cpp.

double QwtSpline::value (  double  x  )  const

Calculate the interpolated function value corresponding to a given argument x. Definition at line 190 of file qwt_spline.cpp. References d_data.

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