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


QwtSpline -


#include <qwt_spline.h> Public Types enum SplineType { Natural, Periodic } Public Member Functions 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 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; } Constructor & Destructor Documentation QwtSpline::QwtSpline (const QwtSpline &other) Copy constructor Parameters: other Spline used for initilization 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 QwtSpline & QwtSpline::operator= (const QwtSpline &other) Assignment operator Parameters: other Spline used for initilization QPolygonF QwtSpline::points () const Return points passed by setPoints 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 Generated automatically by Doxygen for Qwt User's Guide from the source code. Version 5.2.3 Tue Nov 20 2012 QwtSpline(3)

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