QwtSyntheticPointData Class Reference

Synthetic point data. More...

#include <qwt_point_data.h>

Inheritance diagram for QwtSyntheticPointData:

Public Member Functions
	QwtSyntheticPointData (size_t size, const QwtInterval &=QwtInterval())
void	setSize (size_t size)
virtual size_t	size () const
void	setInterval (const QwtInterval &)
QwtInterval	interval () const
virtual QRectF	boundingRect () const
	Calculate the bounding rectangle. More...
virtual QPointF	sample (size_t i) const
virtual double	y (double x) const =0
virtual double	x (uint index) const
virtual void	setRectOfInterest (const QRectF &)
QRectF	rectOfInterest () const
Public Member Functions inherited from QwtSeriesData< QPointF >
	QwtSeriesData ()
	Constructor.
virtual	~QwtSeriesData ()
	Destructor.

Additional Inherited Members
Protected Attributes inherited from QwtSeriesData< QPointF >
QRectF	d_boundingRect
	Can be used to cache a calculated bounding rectangle.

Detailed Description

Synthetic point data.

QwtSyntheticPointData provides a fixed number of points for an interval. The points are calculated in equidistant steps in x-direction.

If the interval is invalid, the points are calculated for the "rectangle of interest", what normally is the displayed area on the plot canvas. In this mode you get different levels of detail, when zooming in/out.

Example

The following example shows how to implement a sinus curve.

#include <cmath>
#include <qwt_series_data.h>
#include <qwt_plot_curve.h>
#include <qwt_plot.h>
#include <qapplication.h>

class SinusData: public QwtSyntheticPointData
{
public:
    SinusData():
        QwtSyntheticPointData( 100 )
    {
    }

    virtual double y( double x ) const
    {
        return qSin( x );
    }
};

int main(int argc, char **argv)
{
    QApplication a( argc, argv );

    QwtPlot plot;
    plot.setAxisScale( QwtPlot::xBottom, 0.0, 10.0 );
    plot.setAxisScale( QwtPlot::yLeft, -1.0, 1.0 );

    QwtPlotCurve *curve = new QwtPlotCurve( "y = sin(x)" );
    curve->setData( new SinusData() );
    curve->attach( &plot );

    plot.show();
    return a.exec();
}

Constructor & Destructor Documentation

QwtSyntheticPointData::QwtSyntheticPointData	(	size_t	size,
		const QwtInterval &	interval = QwtInterval()
	)

Constructor

Parameters

size	Number of points
interval	Bounding interval for the points

See Also

setInterval(), setSize()

Member Function Documentation

QRectF QwtSyntheticPointData::boundingRect ( ) const

virtual

Calculate the bounding rectangle.

This implementation iterates over all points, what could often be implemented much faster using the characteristics of the series. When there are many points it is recommended to overload and reimplement this method using the characteristics of the series ( if possible ).

Returns

Bounding rectangle

Implements QwtSeriesData< QPointF >.

QwtInterval QwtSyntheticPointData::interval

(

)

const

Returns

Bounding interval

See Also

setInterval(), size()

QRectF QwtSyntheticPointData::rectOfInterest

(

)

const

Returns

"rectangle of interest"

See Also

setRectOfInterest()

QPointF QwtSyntheticPointData::sample ( size_t  index ) const

virtual

Calculate the point from an index

Parameters

index

Index

Returns

QPointF(x(index), y(x(index)));

Warning

For invalid indices ( index < 0 || index >= size() ) (0, 0) is returned.

Implements QwtSeriesData< QPointF >.

void QwtSyntheticPointData::setInterval

(

const QwtInterval &

interval

)

Set the bounding interval

Parameters

interval

Interval

See Also

interval(), setSize()

void QwtSyntheticPointData::setRectOfInterest ( const QRectF &  rect )

virtual

Set a the "rectangle of interest"

QwtPlotSeriesItem defines the current area of the plot canvas as "rect of interest" ( QwtPlotSeriesItem::updateScaleDiv() ).

If interval().isValid() == false the x values are calculated in the interval rect.left() -> rect.right().

See Also

rectOfInterest()

Reimplemented from QwtSeriesData< QPointF >.

void QwtSyntheticPointData::setSize

(

size_t

size

)

Change the number of points

Parameters

size	Number of points

See Also

size(), setInterval()

size_t QwtSyntheticPointData::size ( ) const

virtual

Returns

Number of points

See Also

setSize(), interval()

Implements QwtSeriesData< QPointF >.

double QwtSyntheticPointData::x ( uint  index ) const

virtual

Calculate a x-value from an index

x values are calculated by dividing an interval into equidistant steps. If !interval().isValid() the interval is calculated from the "rectangle of interest".

Parameters

index

Index of the requested point

Returns

Calculated x coordinate

See Also

interval(), rectOfInterest(), y()

virtual double QwtSyntheticPointData::y ( double  x ) const

pure virtual

Calculate a y value for a x value

Parameters

x

x value

Returns

Corresponding y value