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

QwtPlotCurve -

#include <qwt_plot_curve.h>
Inherits QwtPlotItem.


enum CurveAttribute { Inverted = 1, Fitted = 2 }
 
enum CurveStyle { NoCurve, Lines, Sticks, Steps, Dots, UserCurve = 100 }
 
enum CurveType { Yfx, Xfy }
 
enum PaintAttribute { PaintFiltered = 1, ClipPolygons = 2 }
 


QwtPlotCurve ()
 
QwtPlotCurve (const QwtText &title)
 
QwtPlotCurve (const QString &title)
 
virtual ~QwtPlotCurve ()
 
double baseline () const
 
virtual QwtDoubleRect boundingRect () const
 
const QBrush & brush () const
 
int closestPoint (const QPoint &pos, double *dist=NULL) const
 
QwtCurveFitter * curveFitter () const
 
CurveType curveType () const
 
QwtData & data ()
 
const QwtData & data () const
 
int dataSize () const
 
virtual void draw (QPainter *p, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRect &) const
 
virtual void draw (QPainter *p, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
 
void draw (int from, int to) const
 
double maxXValue () const
 
double maxYValue () const
 
double minXValue () const
 
double minYValue () const
 
const QPen & pen () const
 
virtual int rtti () const
 
void setBaseline (double ref)
 
void setBrush (const QBrush &)
 
void setCurveAttribute (CurveAttribute, bool on=true)
 
void setCurveFitter (QwtCurveFitter *)
 
void setCurveType (CurveType)
 
void setData (const double *xData, const double *yData, int size)
 
void setData (const QwtArray< double > &xData, const QwtArray< double > &yData)
 
void setData (const QPolygonF &data)
 
void setData (const QwtData &data)
 
void setPaintAttribute (PaintAttribute, bool on=true)
 
void setPen (const QPen &)
 
void setRawData (const double *x, const double *y, int size)
 
void setStyle (CurveStyle style)
 
void setSymbol (const QwtSymbol &s)
 
CurveStyle style () const
 
const QwtSymbol & symbol () const
 
bool testCurveAttribute (CurveAttribute) const
 
bool testPaintAttribute (PaintAttribute) const
 
virtual void updateLegend (QwtLegend *) const
 
double x (int i) const
 
double y (int i) const
 


void closePolyline (const QwtScaleMap &, const QwtScaleMap &, QwtPolygon &) const
 
virtual void drawCurve (QPainter *p, int style, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
 
void drawDots (QPainter *p, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
 
void drawLines (QPainter *p, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
 
void drawSteps (QPainter *p, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
 
void drawSticks (QPainter *p, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
 
virtual void drawSymbols (QPainter *p, const QwtSymbol &, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
 
void fillCurve (QPainter *, const QwtScaleMap &, const QwtScaleMap &, QwtPolygon &) const
 
void init ()
 

A plot item, that represents a series of points.
A curve is the representation of a series of points in the x-y plane. It supports different display styles, interpolation ( f.e. spline ) and symbols.
Usage
a) Assign curve properties
When a curve is created, it is configured to draw black solid lines with in Lines style and no symbols. You can change this by calling setPen(), setStyle() and setSymbol().
b) Connect/Assign data.
QwtPlotCurve gets its points using a QwtData object offering a bridge to the real storage of the points ( like QAbstractItemModel ). There are several convenience classes derived from QwtData, that also store the points inside ( like QStandardItemModel ). QwtPlotCurve also offers a couple of variations of setData(), that build QwtData objects from arrays internally.
c) Attach the curve to a plot
See QwtPlotItem::attach()
Example:
see examples/bode
See also:
QwtPlot, QwtData, QwtSymbol, QwtScaleMap

Attribute for drawing the curve
Fitted ( in combination with the Lines QwtPlotCurve::CurveStyle only )
 

A QwtCurveFitter tries to interpolate/smooth the curve, before it is painted. Note that curve fitting requires temorary memory for calculating coefficients and additional points. If painting in Fitted mode is slow it might be better to fit the points, before they are passed to QwtPlotCurve.
Inverted
 

For Steps only. Draws a step function from the right to the left.
See also:
setCurveAttribute(), testCurveAttribute(), curveFitter()

Curve styles.
NoCurve
 

Don't draw a curve. Note: This doesn't affect the symbols.
Lines
 

Connect the points with straight lines. The lines might be interpolated depending on the 'Fitted' attribute. Curve fitting can be configured using setCurveFitter().
Sticks
 

Draw vertical(Yfx) or horizontal(Xfy) sticks from a baseline which is defined by setBaseline().
Steps
 

Connect the points with a step function. The step function is drawn from the left to the right or vice versa, depending on the 'Inverted' attribute.
Dots
 

Draw dots at the locations of the data points. Note: This is different from a dotted line (see setPen()), and faster as a curve in NoStyle style and a symbol painting a point.
UserCurve
 

Styles >= UserCurve are reserved for derived classes of QwtPlotCurve that overload drawCurve() with additional application specific curve types.
See also:
setStyle(), style()

Curve type.
Yfx
 

Draws y as a function of x (the default). The baseline is interpreted as a horizontal line with y = baseline().
Xfy
 

Draws x as a function of y. The baseline is interpreted as a vertical line with x = baseline().
The baseline is used for aligning the sticks, or filling the curve with a brush.
See also:
setCurveType(), curveType(), baseline() brush()

Attributes to modify the drawing algorithm.
PaintFiltered
 

Tries to reduce the data that has to be painted, by sorting out duplicates, or paintings outside the visible area. Might have a notable impact on curves with many close points. Only a couple of very basic filtering algos are implemented.
ClipPolygons
 

Clip polygons before painting them. In situations, where points are far outside the visible area (f.e when zooming deep) this might be a substantial improvement for the painting performance ( especially on Windows ).
The default is, that no paint attributes are enabled.
See also:
setPaintAttribute(), testPaintAttribute()

Constructor
Parameters:
title Title of the curve

Constructor
Parameters:
title Title of the curve

Return the value of the baseline
See also:
setBaseline()

Returns the bounding rectangle of the curve data. If there is no bounding rect, like for empty data the rectangle is invalid.
See also:
QwtData::boundingRect(), QwtDoubleRect::isValid()
Reimplemented from QwtPlotItem.

Return the brush used to fill the area between lines and the baseline. See also:
setBrush(), setBaseline(), baseline()

Complete a polygon to be a closed polygon including the area between the original polygon and the baseline. Parameters:
xMap X map
 
yMap Y map
 
pa Polygon to be completed

Find the closest curve point for a specific position
Parameters:
pos Position, where to look for the closest curve point
 
dist If dist != NULL, closestPoint() returns the distance between the position and the clostest curve point
Returns:
Index of the closest curve point, or -1 if none can be found ( f.e when the curve has no points )
Note:
closestPoint() implements a dumb algorithm, that iterates over all points

Get the curve fitter. If curve fitting is disabled NULL is returned.
Returns:
Curve fitter

Return the curve type
See also:
CurveType, setCurveType()

Returns:
the the curve data

Returns:
the the curve data

Return the size of the data arrays
See also:
setData()

Draw the complete curve. Parameters:
painter Painter
 
xMap Maps x-values into pixel coordinates.
 
yMap Maps y-values into pixel coordinates.
See also:
drawCurve(), drawSymbols()
Implements QwtPlotItem.

Draw an interval of the curve. Parameters:
painter Painter
 
xMap maps x-values into pixel coordinates.
 
yMap maps y-values into pixel coordinates.
 
from index of the first point to be painted
 
to index of the last point to be painted. If to < 0 the curve will be painted to its last point.
See also:
drawCurve(), drawSymbols(),

Draw a set of points of a curve. When observing an measurement while it is running, new points have to be added to an existing curve. drawCurve can be used to display them avoiding a complete redraw of the canvas.
Setting plot()->canvas()->setAttribute(Qt::WA_PaintOutsidePaintEvent, true); will result in faster painting, if the paint engine of the canvas widget supports this feature.
Parameters:
from Index of the first point to be painted
 
to Index of the last point to be painted. If to < 0 the curve will be painted to its last point.
See also:
drawCurve(), drawSymbols()

Draw the line part (without symbols) of a curve interval. Parameters:
painter Painter
 
style curve style, see QwtPlotCurve::CurveStyle
 
xMap x map
 
yMap y map
 
from index of the first point to be painted
 
to index of the last point to be painted
See also:
draw(), drawDots(), drawLines(), drawSteps(), drawSticks()

Draw dots
Parameters:
painter Painter
 
xMap x map
 
yMap y map
 
from index of the first point to be painted
 
to index of the last point to be painted
See also:
draw(), drawCurve(), drawSticks(), drawLines(), drawSteps()

Draw lines. If the CurveAttribute Fitted is enabled a QwtCurveFitter tries to interpolate/smooth the curve, before it is painted.
Parameters:
painter Painter
 
xMap x map
 
yMap y map
 
from index of the first point to be painted
 
to index of the last point to be painted
See also:
setCurveAttribute(), setCurveFitter(), draw(), drawLines(), drawDots(), drawSteps(), drawSticks()

Draw step function
The direction of the steps depends on Inverted attribute.
Parameters:
painter Painter
 
xMap x map
 
yMap y map
 
from index of the first point to be painted
 
to index of the last point to be painted
See also:
CurveAttribute, setCurveAttribute(), draw(), drawCurve(), drawDots(), drawLines(), drawSticks()

Draw sticks
Parameters:
painter Painter
 
xMap x map
 
yMap y map
 
from index of the first point to be painted
 
to index of the last point to be painted
See also:
draw(), drawCurve(), drawDots(), drawLines(), drawSteps()

Draw symbols. Parameters:
painter Painter
 
symbol Curve symbol
 
xMap x map
 
yMap y map
 
from index of the first point to be painted
 
to index of the last point to be painted
See also:
setSymbol(), draw(), drawCurve()

Fill the area between the curve and the baseline with the curve brush
Parameters:
painter Painter
 
xMap x map
 
yMap y map
 
pa Polygon
See also:
setBrush(), setBaseline(), setCurveType()

Return the pen used to draw the lines. See also:
setPen(), brush()

Returns:
QwtPlotItem::Rtti_PlotCurve
Reimplemented from QwtPlotItem.

Set the value of the baseline. The baseline is needed for filling the curve with a brush or the Sticks drawing style. The default value is 0.0. The interpretation of the baseline depends on the CurveType. With QwtPlotCurve::Yfx, the baseline is interpreted as a horizontal line at y = baseline(), with QwtPlotCurve::Yfy, it is interpreted as a vertical line at x = baseline().
Parameters:
reference baseline
See also:
baseline(), setBrush(), setStyle(), setCurveType()

Assign a brush. In case of brush.style() != QBrush::NoBrush and style() != QwtPlotCurve::Sticks the area between the curve and the baseline will be filled.
In case !brush.color().isValid() the area will be filled by pen.color(). The fill algorithm simply connects the first and the last curve point to the baseline. So the curve data has to be sorted (ascending or descending).
Parameters:
brush New brush
See also:
brush(), setBaseline(), baseline()

Specify an attribute for drawing the curve
Parameters:
attribute Curve attribute
 
on On/Off
/sa CurveAttribute, testCurveAttribute(), setCurveFitter()

Assign a curve fitter setCurveFitter(NULL) disables curve fitting.
Parameters:
curveFitter Curve fitter

Assign the curve type
Parameters:
curveType Yfx or Xfy
See also:
CurveType, curveType()

Set data by copying x- and y-values from specified memory blocks. Contrary to setCurveRawData(), this function makes a 'deep copy' of the data.
Parameters:
xData Pointer to x values
 
yData Pointer to y values
 
size Size of xData and yData
Note:
Internally the data is stored in a QwtArrayData object

Initialize data with x- and y-arrays (explicitly shared) ( Builds an QwtArrayData object internally )
Parameters:
xData x data
 
yData y data
Note:
Internally the data is stored in a QwtArrayData object

Initialize data with an array of points (explicitly shared).
Parameters:
data Data
Note:
Internally the data is stored in a QwtPolygonFData object

Initialize data with a pointer to QwtData.
Parameters:
data Data
See also:
QwtData::copy()

Specify an attribute how to draw the curve
Parameters:
attribute Paint attribute
 
on On/Off /sa PaintAttribute, testPaintAttribute()

Assign a pen
The width of non cosmetic pens is scaled according to the resolution of the paint device.
Parameters:
pen New pen
See also:
pen(), brush(), QwtPainter::scaledPen()

Initialize the data by pointing to memory blocks which are not managed by QwtPlotCurve. setRawData is provided for efficiency. It is important to keep the pointers during the lifetime of the underlying QwtCPointerData class.
Parameters:
xData pointer to x data
 
yData pointer to y data
 
size size of x and y
Note:
Internally the data is stored in a QwtCPointerData object

Set the curve's drawing style
Parameters:
style Curve style
See also:
CurveStyle, style()

Assign a symbol. Parameters:
symbol Symbol
See also:
symbol()

Return the current style
See also:
CurveStyle, setStyle()

Return the current symbol. See also:
setSymbol()

Returns:
true, if attribute is enabled
See also:
CurveAttribute, setCurveAttribute()

Return the current paint attributes. See also:
PaintAttribute, setPaintAttribute()

Parameters:
i index
Returns:
x-value at position i

Parameters:
i index
Returns:
y-value at position i

Generated automatically by Doxygen for Qwt User's Guide from the source code.
Tue Nov 20 2012 Version 5.2.3

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