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Man Pages
QwtSpline(3) Qwt User's Guide QwtSpline(3)

QwtSpline -

#include <qwt_spline.h>


enum SplineType { Natural, Periodic }
 


QwtSpline ()
 
QwtSpline (const QwtSpline &)
 
~QwtSpline ()
 
const QwtArray< double > & coefficientsA () const
 
const QwtArray< double > & coefficientsB () const
 
const QwtArray< double > & coefficientsC () const
 
bool isValid () const
 
QwtSpline & operator= (const QwtSpline &)
 
QPolygonF points () const
 
void reset ()
 
bool setPoints (const QPolygonF &points)
 
void setSplineType (SplineType)
 
SplineType splineType () const
 
double value (double x) const
 


bool buildNaturalSpline (const QPolygonF &)
 
bool buildPeriodicSpline (const QPolygonF &)
 


PrivateData * d_data
 

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; }

Copy constructor
Parameters:
other Spline used for initilization

Determines the coefficients for a natural spline. Returns:
true if successful

Determines the coefficients for a periodic spline. Returns:
true if successful

Returns:
A coefficients

Returns:
B coefficients

Returns:
C coefficients

Assignment operator
Parameters:
other Spline used for initilization

Return points passed by setPoints

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:
points Points
Returns:
true if successful
Warning:
The sequence of x (but not y) values has to be strictly monotone increasing, which means points[i].x() < points[i+1].x(). If this is not the case, the function will return false

Select the algorithm used for calculating the spline
Parameters:
splineType Spline type
See also:
splineType()

Returns:
the spline type
See also:
setSplineType()

Calculate the interpolated function value corresponding to a given argument x.

Generated automatically by Doxygen for Qwt User's Guide from the source code.
Tue Nov 20 2012 Version 5.2.3

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