Sources_For_Linux/Qwt/doc/man/man3/QwtSpline.3

.TH "QwtSpline" 3 "Mon Dec 28 2020" "Version 6.1.6" "Qwt User's Guide" \" -*- nroff -*-
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.SH NAME
QwtSpline \- A class for spline interpolation\&.  

.SH SYNOPSIS
.br
.PP
.PP
\fC#include <qwt_spline\&.h>\fP
.SS "Public Types"

.in +1c
.ti -1c
.RI "enum \fBSplineType\fP { \fBNatural\fP, \fBPeriodic\fP }"
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.RI "Spline type\&. "
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.SS "Public Member Functions"

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.RI "\fBQwtSpline\fP ()"
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.RI "Constructor\&. "
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.RI "\fBQwtSpline\fP (const \fBQwtSpline\fP &)"
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.RI "\fB~QwtSpline\fP ()"
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.RI "Destructor\&. "
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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 &\fBpoints\fP)"
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.RI "Calculate the spline coefficients\&. "
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.RI "QPolygonF \fBpoints\fP () const"
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.RI "void \fBreset\fP ()"
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.RI "Free allocated memory and set size to 0\&. "
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.RI "bool \fBisValid\fP () const"
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.RI "True if valid\&. "
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.RI "double \fBvalue\fP (double x) const"
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.RI "const QVector< double > & \fBcoefficientsA\fP () const"
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.RI "const QVector< double > & \fBcoefficientsB\fP () const"
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.RI "const QVector< double > & \fBcoefficientsC\fP () const"
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.SS "Protected Member Functions"

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.RI "bool \fBbuildNaturalSpline\fP (const QPolygonF &)"
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.RI "Determines the coefficients for a natural spline\&. "
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.RI "bool \fBbuildPeriodicSpline\fP (const QPolygonF &)"
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.RI "Determines the coefficients for a periodic spline\&. "
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.SH "Detailed Description"
.PP 
A class for spline interpolation\&. 

The \fBQwtSpline\fP class is used for cubical spline interpolation\&. Two types of splines, natural and periodic, are supported\&.
.PP
\fBUsage:\fP
.RS 4

.PD 0

.IP "1." 4
First call \fBsetPoints()\fP to determine the spline coefficients for a tabulated function y(x)\&. 
.IP "2." 4
After the coefficients have been set up, the interpolated function value for an argument x can be determined by calling \fBQwtSpline::value()\fP\&. 
.PP
.RE
.PP
\fBExample:\fP
.RS 4

.PP
.nf
#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;
}

.fi
.PP
 
.RE
.PP

.SH "Member Enumeration Documentation"
.PP 
.SS "enum \fBQwtSpline::SplineType\fP"

.PP
Spline type\&. 
.PP
\fBEnumerator\fP
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.TP
\fB\fINatural \fP\fP
A natural spline\&. 
.TP
\fB\fIPeriodic \fP\fP
A periodic spline\&. 
.SH "Constructor & Destructor Documentation"
.PP 
.SS "QwtSpline::QwtSpline (const \fBQwtSpline\fP & other)"
Copy constructor 
.PP
\fBParameters\fP
.RS 4
\fIother\fP Spline used for initialization 
.RE
.PP

.SH "Member Function Documentation"
.PP 
.SS "bool QwtSpline::buildNaturalSpline (const QPolygonF & points)\fC [protected]\fP"

.PP
Determines the coefficients for a natural spline\&. 
.PP
\fBReturns\fP
.RS 4
true if successful 
.RE
.PP

.SS "bool QwtSpline::buildPeriodicSpline (const QPolygonF & points)\fC [protected]\fP"

.PP
Determines the coefficients for a periodic spline\&. 
.PP
\fBReturns\fP
.RS 4
true if successful 
.RE
.PP

.SS "const QVector< double > & QwtSpline::coefficientsA () const"

.PP
\fBReturns\fP
.RS 4
A coefficients 
.RE
.PP

.SS "const QVector< double > & QwtSpline::coefficientsB () const"

.PP
\fBReturns\fP
.RS 4
B coefficients 
.RE
.PP

.SS "const QVector< double > & QwtSpline::coefficientsC () const"

.PP
\fBReturns\fP
.RS 4
C coefficients 
.RE
.PP

.SS "\fBQwtSpline\fP & QwtSpline::operator= (const \fBQwtSpline\fP & other)"
Assignment operator 
.PP
\fBParameters\fP
.RS 4
\fIother\fP Spline used for initialization 
.RE
.PP
\fBReturns\fP
.RS 4
*this 
.RE
.PP

.SS "QPolygonF QwtSpline::points () const"

.PP
\fBReturns\fP
.RS 4
Points, that have been by \fBsetPoints()\fP 
.RE
.PP

.SS "bool QwtSpline::setPoints (const QPolygonF & points)"

.PP
Calculate the spline coefficients\&. Depending on the value of \fIperiodic\fP, this function will determine the coefficients for a natural or a periodic spline and store them internally\&.
.PP
\fBParameters\fP
.RS 4
\fIpoints\fP Points 
.RE
.PP
\fBReturns\fP
.RS 4
true if successful 
.RE
.PP
\fBWarning\fP
.RS 4
The sequence of x (but not y) values has to be strictly monotone increasing, which means \fCpoints[i]\&.x() < points[i+1]\&.x()\fP\&. If this is not the case, the function will return false 
.RE
.PP

.SS "void QwtSpline::setSplineType (\fBSplineType\fP splineType)"
Select the algorithm used for calculating the spline
.PP
\fBParameters\fP
.RS 4
\fIsplineType\fP Spline type 
.RE
.PP
\fBSee also\fP
.RS 4
\fBsplineType()\fP 
.RE
.PP

.SS "\fBQwtSpline::SplineType\fP QwtSpline::splineType () const"

.PP
\fBReturns\fP
.RS 4
the spline type 
.RE
.PP
\fBSee also\fP
.RS 4
\fBsetSplineType()\fP 
.RE
.PP

.SS "double QwtSpline::value (double x) const"
Calculate the interpolated function value corresponding to a given argument x\&.
.PP
\fBParameters\fP
.RS 4
\fIx\fP Coordinate 
.RE
.PP
\fBReturns\fP
.RS 4
Interpolated coordinate 
.RE
.PP


.SH "Author"
.PP 
Generated automatically by Doxygen for Qwt User's Guide from the source code\&.