QwtSpline - Man Page
Name
QwtSpline —
A class for spline interpolation.
Synopsis
#include <qwt_spline.h>
Public Types
enum SplineType { Natural, Periodic }
Public Member Functions
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
QwtSpline ()
QwtSpline (const QwtSpline &)
void reset ()
bool setPoints (const QPolygonF &points)
void setSplineType (SplineType)
SplineType splineType () const
double value (double x) const
~QwtSpline ()
Protected Member Functions
bool buildNaturalSpline (const QPolygonF &)
bool buildPeriodicSpline (const QPolygonF &)
Protected Attributes
PrivateData * d_data
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:
- First call setPoints() to determine the spline coefficients for a tabulated function y(x).
- 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;
}Member Enumeration Documentation
enum QwtSpline::SplineType
Spline type.
Constructor & Destructor Documentation
QwtSpline::QwtSpline ()
Constructor.
QwtSpline::QwtSpline (const QwtSpline &other) Copy constructor
- Parameters:
other Spline used for initilization
QwtSpline::~QwtSpline ()
Destructor.
Member Function Documentation
bool QwtSpline::buildNaturalSpline (const QPolygonF &points) [protected]
Determines the coefficients for a natural spline. Returns:
true if successful
bool QwtSpline::buildPeriodicSpline (const QPolygonF &points) [protected]
Determines the coefficients for a periodic spline. Returns:
true if successful
const QwtArray< double > & QwtSpline::coefficientsA () const Returns
A coefficients
const QwtArray< double > & QwtSpline::coefficientsB () const Returns
B coefficients
const QwtArray< double > & QwtSpline::coefficientsC () const Returns
C coefficients
bool QwtSpline::isValid () const
True if valid.
QwtSpline & QwtSpline::operator= (const QwtSpline &other) Assignment operator
- Parameters:
other Spline used for initilization
QPolygonF QwtSpline::points () const Return points passed by setPoints
void QwtSpline::reset ()
Free allocated memory and set size to 0.
bool QwtSpline::setPoints (const QPolygonF &points)
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
void QwtSpline::setSplineType (SplineTypesplineType) Select the algorithm used for calculating the spline
- Parameters:
splineType Spline type
- See also:
splineType()
QwtSpline::SplineType QwtSpline::splineType () const Returns
the spline type
See also:
setSplineType()
double QwtSpline::value (doublex) const Calculate the interpolated function value corresponding to a given argument x.
Author
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