QwtSplinePolynomial Class Reference

A cubic polynomial without constant term. More...

#include <qwt_spline_polynomial.h>

List of all members.

Public Member Functions
double	curvatureAt (double x) const
bool	operator!= (const QwtSplinePolynomial &) const
bool	operator== (const QwtSplinePolynomial &) const
	QwtSplinePolynomial (double c3=0.0, double c2=0.0, double c1=0.0)
	Constructor.
double	slopeAt (double x) const
double	valueAt (double x) const
Static Public Member Functions
static QwtSplinePolynomial	fromCurvatures (const QPointF &p1, double cv1, const QPointF &p2, double cv2)
static QwtSplinePolynomial	fromCurvatures (double dx, double dy, double cv1, double cv2)
static QwtSplinePolynomial	fromSlopes (const QPointF &p1, double m1, const QPointF &p2, double m2)
static QwtSplinePolynomial	fromSlopes (double x, double y, double m1, double m2)
Public Attributes
double	c1
	coefficient of the linear summand
double	c2
	coefficient of the quadratic summand
double	c3
	coefficient of the cubic summand

---

Detailed Description

A cubic polynomial without constant term.

QwtSplinePolynomial is a 3rd degree polynomial of the form: y = c3 * x³ + c2 * x² + c1 * x;

QwtSplinePolynomial is usually used in combination with polygon interpolation, where it is not necessary to store a constant term ( c0 ), as the translation is known from the corresponding polygon points.

See also:

QwtSplineC1

Definition at line 33 of file qwt_spline_polynomial.h.

---

Constructor & Destructor Documentation

QwtSplinePolynomial::QwtSplinePolynomial	(	double	a3 = 0.0,
		double	a2 = 0.0,
		double	a1 = 0.0
	)		[inline]

Constructor.

Parameters:

a3	Coefficient of the cubic summand
a2	Coefficient of the quadratic summand
a1	Coefficient of the linear summand

Definition at line 77 of file qwt_spline_polynomial.h.

---

Member Function Documentation

double QwtSplinePolynomial::curvatureAt

(

double

x

)

const [inline]

Calculate the value of the second derivate of a polynomial for a given x

Parameters:

x

Parameter

Returns:

Curvature at x

Definition at line 130 of file qwt_spline_polynomial.h.

QwtSplinePolynomial QwtSplinePolynomial::fromCurvatures	(	const QPointF &	p1,
		double	cv1,
		const QPointF &	p2,
		double	cv2
	)		[inline, static]

Find the coefficients for the polynomial including 2 points with specific values for the 2nd derivates at these points.

Parameters:

p1	First point
cv1	Value of the second derivate at p1
p2	Second point
cv2	Value of the second derivate at p2

Returns:

Coefficients of the polynomials

Note:

The missing constant term of the polynomial is p1.y()

Definition at line 185 of file qwt_spline_polynomial.h.

QwtSplinePolynomial QwtSplinePolynomial::fromCurvatures	(	double	x,
		double	y,
		double	cv1,
		double	cv2
	)		[inline, static]

Find the coefficients for the polynomial from the offset between 2 points and specific values for the 2nd derivates at these points.

Parameters:

dx	X-offset
dy	Y-offset
cv1	Value of the second derivate at p1
cv2	Value of the second derivate at p2

Returns:

Coefficients of the polynomials

Definition at line 202 of file qwt_spline_polynomial.h.

QwtSplinePolynomial QwtSplinePolynomial::fromSlopes	(	const QPointF &	p1,
		double	m1,
		const QPointF &	p2,
		double	m2
	)		[inline, static]

Find the coefficients for the polynomial including 2 points with specific values for the 1st derivates at these points.

Parameters:

p1	First point
m1	Value of the first derivate at p1
p2	Second point
m2	Value of the first derivate at p2

Returns:

Coefficients of the polynomials

Note:

The missing constant term of the polynomial is p1.y()

Definition at line 147 of file qwt_spline_polynomial.h.

QwtSplinePolynomial QwtSplinePolynomial::fromSlopes	(	double	dx,
		double	dy,
		double	m1,
		double	m2
	)		[inline, static]

Find the coefficients for the polynomial from the offset between 2 points and specific values for the 1st derivates at these points.

Parameters:

dx	X-offset
dy	Y-offset
m1	Value of the first derivate at p1
m2	Value of the first derivate at p2

Returns:

Coefficients of the polynomials

Definition at line 164 of file qwt_spline_polynomial.h.

bool QwtSplinePolynomial::operator!=

(

const QwtSplinePolynomial &

other

)

const [inline]

Parameters:

other

Other polynomial

Returns:

true, when the polynomials have different coefficients

Definition at line 97 of file qwt_spline_polynomial.h.

bool QwtSplinePolynomial::operator==

(

const QwtSplinePolynomial &

other

)

const [inline]

Parameters:

other

Other polynomial

Returns:

true, when both polynomials have the same coefficients

Definition at line 88 of file qwt_spline_polynomial.h.

double QwtSplinePolynomial::slopeAt

(

double

x

)

const [inline]

Calculate the value of the first derivate of a polynomial for a given x

Parameters:

x

Parameter

Returns:

Slope at x

Definition at line 119 of file qwt_spline_polynomial.h.

double QwtSplinePolynomial::valueAt

(

double

x

)

const [inline]

Calculate the value of a polynomial for a given x

Parameters:

x

Parameter

Returns:

Value at x

Definition at line 108 of file qwt_spline_polynomial.h.

---

Member Data Documentation

double QwtSplinePolynomial::c1

coefficient of the linear summand

Definition at line 67 of file qwt_spline_polynomial.h.

double QwtSplinePolynomial::c2

coefficient of the quadratic summand

Definition at line 64 of file qwt_spline_polynomial.h.

double QwtSplinePolynomial::c3

coefficient of the cubic summand

Definition at line 61 of file qwt_spline_polynomial.h.

---

The documentation for this class was generated from the following file:

• qwt_spline_polynomial.h