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:
-
- 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; }
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 () constReturns:
- A coefficients
const QwtArray< double > & QwtSpline::coefficientsB () constReturns:
- B coefficients
const QwtArray< double > & QwtSpline::coefficientsC () constReturns:
- 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 () constReturn 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 () constReturns:
- the spline type
See also:
- setSplineType()
double QwtSpline::value (doublex) constCalculate the interpolated function value corresponding to a given argument x.
Author
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