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.TH "QwtSpline" 3 "24 May 2008" "Version 5.1.1" "Qwt User's Guide" \" -*- nroff -*-
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.SH "Detailed Description"
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A class for spline interpolation.
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The \fBQwtSpline\fP class is used for cubical spline interpolation. Two types of splines, natural and periodic, are supported.
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First call \fBsetPoints()\fP to determine the spline coefficients for a tabulated function y(x).
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After the coefficients have been set up, the interpolated function value for an argument x can be determined by calling \fBQwtSpline::value()\fP.
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#include <qwt_spline.h>
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QPolygonF interpolate(const QPolygonF& points, int numValues)
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if ( !spline.setPoints(points) )
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QPolygonF interpolatedPoints(numValues);
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(points[numPoints - 1].x() - points[0].x()) / (points.size() - 1);
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for(i = 0; i < points.size(); i++) / interpolate
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const double x = points[0].x() + i * delta;
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interpolatedPoints[i].setX(x);
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interpolatedPoints[i].setY(spline.value(x));
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return interpolatedPoints;
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Definition at line 77 of file qwt_spline.h.
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.RI "enum \fBSplineType\fP { \fBNatural\fP, \fBPeriodic\fP }"
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.SS "Public Member Functions"
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.RI "\fBQwtSpline\fP ()"
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.RI "\fBQwtSpline\fP (const \fBQwtSpline\fP &)"
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.RI "\fB~QwtSpline\fP ()"
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.RI "\fBQwtSpline\fP & \fBoperator=\fP (const \fBQwtSpline\fP &)"
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.RI "void \fBsetSplineType\fP (\fBSplineType\fP)"
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.RI "\fBSplineType\fP \fBsplineType\fP () const"
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.RI "bool \fBsetPoints\fP (const QPolygonF &points)"
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.RI "QPolygonF \fBpoints\fP () const"
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.RI "void \fBreset\fP ()"
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.RI "bool \fBisValid\fP () const"
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.RI "double \fBvalue\fP (double x) const"
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.SS "Protected Member Functions"
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.RI "bool \fBbuildNaturalSpline\fP (const QPolygonF &)"
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.RI "bool \fBbuildPeriodicSpline\fP (const QPolygonF &)"
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.SS "Protected Attributes"
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.RI "PrivateData * \fBd_data\fP"
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.SH "Constructor & Destructor Documentation"
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.SS "QwtSpline::QwtSpline ()"
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Definition at line 73 of file qwt_spline.cpp.
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.SS "QwtSpline::~QwtSpline ()"
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Definition at line 90 of file qwt_spline.cpp.
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.SH "Member Function Documentation"
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.SS "bool QwtSpline::setPoints (const QPolygonF & points)"
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Determine the function table index corresponding to a value x Calculate the spline coefficients.
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Depending on the value of \fIperiodic\fP, this function will determine the coefficients for a natural or a periodic spline and store them internally.
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\fIsize\fP number of points
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\fIperiodic\fP if true, calculate periodic spline
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The sequence of x (but not y) values has to be strictly monotone increasing, which means \fCx[0] < x[1] < .... < x[n-1]\fP. If this is not the case, the function will return false
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Definition at line 126 of file qwt_spline.cpp.
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.SS "QPolygonF QwtSpline::points () const"
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Return points passed by setPoints
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Definition at line 164 of file qwt_spline.cpp.
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.SS "void QwtSpline::reset ()"
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Free allocated memory and set size to 0.
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Definition at line 172 of file qwt_spline.cpp.
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.SS "bool QwtSpline::isValid () const"
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Definition at line 181 of file qwt_spline.cpp.
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.SS "double QwtSpline::value (double x) const"
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Calculate the interpolated function value corresponding to a given argument x.
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Definition at line 190 of file qwt_spline.cpp.
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.SS "bool QwtSpline::buildNaturalSpline (const QPolygonF & points)\fC [protected]\fP"
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Determines the coefficients for a natural spline.
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Definition at line 209 of file qwt_spline.cpp.
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.SS "bool QwtSpline::buildPeriodicSpline (const QPolygonF & points)\fC [protected]\fP"
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Determines the coefficients for a periodic spline.
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Definition at line 292 of file qwt_spline.cpp.
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