---
name: "QwtCurve"
section: "3"
platform: "linux"
package: "libqwt-doc"
version: "4.2.0-6"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/QwtCurve"
---

# QwtCurve(3)

## NAME

QwtCurve -

## SYNOPSIS

Inherited by **QwtPlotCurve**.

## Detailed Description

A class which draws curves.

This class can be used to display data as a curve in the x-y plane. It supports different display styles, spline interpolation and symbols.

**Usage**.RS 4

- **A. Assign curve properties**

  When a curve is created, it is configured to draw black solid lines with QwtCurve::Lines and no symbols. You can change this by calling **QwtCurve::setPen()**, **QwtCurve::setStyle()** and **QwtCurve::setSymbol()**.

- **B. Assign or change data.**

  Data can be set in two ways:.PD 0

- •

  **QwtCurve::setData()** is overloaded to initialize the x and y data by copying from different data structures with different kind of copy semantics.

- •

  **QwtCurve::setRawData()** only stores the pointers and size information and is provided for backwards compatibility. This function is less safe (you must not delete the data while they are attached), but has been more efficient, and has been more convenient for dynamically changing data. Use of **QwtCurve::setData()** in combination with a problem-specific subclass of **QwtData** is always preferrable.

- **C. Draw**

  **QwtCurve::draw()** maps the data into pixel coordinates and paints them.

**Example:**.RS 4 see examples/curvdemo

**See also:**

**QwtData**, **QwtSymbol**, **QwtDiMap**

Definition at line 60 of file qwt\_curve.h.

### Public Types

enum **CurveStyle** { **NoCurve**, **Lines**, **Sticks**, **Steps**, **Dots**, **Spline**, **UserCurve** =  100 }\
 enum **CurveOption** { **Auto** =  0, **Yfx** =  1, **Xfy** =  2, **Parametric** =  4, **Periodic** =  8, **Inverted** =  16 }\

### Public Member Functions

**QwtCurve** (const QString &title=QString::null)\
 **QwtCurve** (const **QwtCurve** &c)\
 virtual **~QwtCurve** ()\
 const **QwtCurve** & **operator=** (const **QwtCurve** &c)\
 void **setRawData** (const double \*x, const double \*y, int size)\
 void **setData** (const double \*xData, const double \*yData, int size)\
 void **setData** (const QwtArray\< double \> &xData, const QwtArray\< double \> &yData)\
 void **setData** (const QwtArray\< **QwtDoublePoint** \> &data)\
 void **setData** (const **QwtData** &data)\
 int **dataSize** () const\
 double **x** (int i) const\
 double **y** (int i) const\
 virtual **QwtDoubleRect** **boundingRect** () const\
 double **minXValue** () const\
 double **maxXValue** () const\
 double **minYValue** () const\
 double **maxYValue** () const\
 void **setOptions** (int t)\
 int **options** () const\
 void **setTitle** (const QString &title)\
 const QString & **title** () const\
 void **setPen** (const QPen &)\
 const QPen & **pen** () const\
 void **setBrush** (const QBrush &)\
 const QBrush & **brush** () const\
 void **setBaseline** (double ref)\
 double **baseline** () const\
 void **setStyle** (int style, int options=0)\
 int **style** () const\
 void **setSymbol** (const **QwtSymbol** &s)\
 const **QwtSymbol** & **symbol** () const\
 void **setSplineSize** (int s)\
 int **splineSize** () const\
 virtual void **draw** (QPainter \*p, const **QwtDiMap** &xMap, const **QwtDiMap** &yMap, int from=0, int to=-1)\

### Protected Member Functions

void **init** (const QString &title)\
 void **copy** (const **QwtCurve** &c)\
 virtual void **drawCurve** (QPainter \*p, int style, const **QwtDiMap** &xMap, const **QwtDiMap** &yMap, int from, int to)\
 virtual void **drawSymbols** (QPainter \*p, **QwtSymbol** &, const **QwtDiMap** &xMap, const **QwtDiMap** &yMap, int from, int to)\
 void **drawLines** (QPainter \*p, const **QwtDiMap** &xMap, const **QwtDiMap** &yMap, int from, int to)\
 void **drawSticks** (QPainter \*p, const **QwtDiMap** &xMap, const **QwtDiMap** &yMap, int from, int to)\
 void **drawDots** (QPainter \*p, const **QwtDiMap** &xMap, const **QwtDiMap** &yMap, int from, int to)\
 void **drawSteps** (QPainter \*p, const **QwtDiMap** &xMap, const **QwtDiMap** &yMap, int from, int to)\
 void **drawSpline** (QPainter \*p, const **QwtDiMap** &xMap, const **QwtDiMap** &yMap)\
 void **closePolyline** (const **QwtDiMap** &, const **QwtDiMap** &, QPointArray &) const\
 virtual void **curveChanged** ()\
 int **verifyRange** (int &i1, int &i2)\

### Protected Attributes

**QwtSpline** **d\_spx**\
 **QwtSpline** **d\_spy**\

## Member Enumeration Documentation

### enum QwtCurve::CurveOption

Curve options.

**See also:**

**QwtCurve::setOptions**

Definition at line 82 of file qwt\_curve.h.

### enum QwtCurve::CurveStyle

Curve styles.

**See also:**

**QwtCurve::setStyle**

Definition at line 67 of file qwt\_curve.h.

## Constructor & Destructor Documentation

### QwtCurve::QwtCurve (const QString & title = `QString::null`)

Ctor.

**Parameters:**

*title* title of the curve

Definition at line 321 of file qwt\_curve.cpp.

References init().

### QwtCurve::QwtCurve (const QwtCurve & c)

Copy Constructor.

Definition at line 60 of file qwt\_curve.cpp.

References copy(), d\_title, and init().

### QwtCurve::~QwtCurve ()` [virtual]`

Dtor.

Definition at line 52 of file qwt\_curve.cpp.

## Member Function Documentation

### double QwtCurve::baseline () const

Return the value of the baseline.

**See also:**

**QwtCurve::setBaseline**

Definition at line 907 of file qwt\_curve.cpp.

Referenced by QwtPlot::curveBaseline().

### QwtDoubleRect QwtCurve::boundingRect () const` [virtual]`

Returns the bounding rectangle of the curve data. If there is no bounding rect, like for empty data the rectangle is invalid: **QwtDoubleRect.isValid()** == FALSE Definition at line 309 of file qwt\_curve.cpp.

References QwtData::boundingRect().

Referenced by QwtPlot::updateAxes().

### const QBrush & QwtCurve::brush () const

Return the brush used to fill the area between lines and the baseline.

**See also:**

**QwtCurve::setBrush**, **QwtCurve::setBaseline**, **QwtCurve::baseline**

Definition at line 196 of file qwt\_curve.cpp.

Referenced by QwtPlot::curveBrush().

### void QwtCurve::closePolyline (const QwtDiMap & xMap, const QwtDiMap & yMap, QPointArray & pa) const` [protected]`

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

Definition at line 831 of file qwt\_curve.cpp.

References QwtDiMap::transform().

Referenced by drawDots(), drawLines(), drawSpline(), and drawSteps().

### void QwtCurve::copy (const QwtCurve & c)` [protected]`

Copy the contents of a curve into another curve.

Definition at line 36 of file qwt\_curve.cpp.

References QwtData::copy(), d\_data, d\_options, d\_pen, d\_ref, d\_splineSize, d\_style, d\_sym, and d\_title.

Referenced by operator=(), and QwtCurve().

### void QwtCurve::curveChanged ()` [protected, virtual]`

Notify a change of attributes. This virtual function is called when an attribute of the curve has changed. It can be redefined by derived classes. The default implementation does nothing.

Reimplemented in **QwtPlotCurve**.

Definition at line 927 of file qwt\_curve.cpp.

Referenced by operator=(), setBaseline(), setBrush(), setData(), setOptions(), setPen(), setRawData(), setSplineSize(), setStyle(), setSymbol(), and setTitle().

### int QwtCurve::dataSize () const

Return the size of the data arrays Definition at line 915 of file qwt\_curve.cpp.

References QwtData::size().

Referenced by QwtPlot::closestCurve(), draw(), drawCurve(), drawSpline(), and verifyRange().

### void QwtCurve::draw (QPainter \* painter, const QwtDiMap & xMap, const QwtDiMap & yMap, int from = `0`, int to = `-1`)` [virtual]`

Draw an intervall 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:**

**QwtCurve::drawCurve**, **QwtCurve::drawDots**, **QwtCurve::drawLines**, **QwtCurve::drawSpline**, **QwtCurve::drawSteps**, **QwtCurve::drawSticks**

Definition at line 357 of file qwt\_curve.cpp.

References dataSize(), drawCurve(), drawSymbols(), QwtSymbol::style(), and verifyRange().

Referenced by QwtPlot::drawCanvasItems(), and QwtPlot::drawCurve().

### void QwtCurve::drawCurve (QPainter \* painter, int style, const QwtDiMap & xMap, const QwtDiMap & yMap, int from, int to)` [protected, virtual]`

Draw the line part (without symbols) of a curve interval.

**Parameters:**

*painter* Painter \
 *style* curve style, see **QwtCurve::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:**

**QwtCurve::draw**, **QwtCurve::drawDots**, **QwtCurve::drawLines**, **QwtCurve::drawSpline**, **QwtCurve::drawSteps**, **QwtCurve::drawSticks**

Definition at line 401 of file qwt\_curve.cpp.

References dataSize(), drawDots(), drawLines(), drawSpline(), drawSteps(), and drawSticks().

Referenced by draw().

### void QwtCurve::drawDots (QPainter \* painter, const QwtDiMap & xMap, const QwtDiMap & yMap, int from, int to)` [protected]`

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:**

QwtCurve::drawPolyline, QwtCurve::drawLine, **QwtCurve::drawLines**, **QwtCurve::drawSpline**, **QwtCurve::drawSteps** QwtCurve::drawPolyline, QwtCurve::drawPolygon

Definition at line 502 of file qwt\_curve.cpp.

References closePolyline(), QwtPainter::drawPoint(), QwtPainter::drawPolygon(), QwtDiMap::transform(), x(), and y().

Referenced by drawCurve().

### void QwtCurve::drawLines (QPainter \* painter, const QwtDiMap & xMap, const QwtDiMap & yMap, int from, int to)` [protected]`

Draw lines.

**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:**

**QwtCurve::draw**, **QwtCurve::drawLines**, **QwtCurve::drawDots**, **QwtCurve::drawSpline**, **QwtCurve::drawSteps**, **QwtCurve::drawSticks**

Definition at line 441 of file qwt\_curve.cpp.

References closePolyline(), QwtPainter::drawPolygon(), QwtPainter::drawPolyline(), QwtDiMap::transform(), x(), and y().

Referenced by drawCurve(), and drawSpline().

### void QwtCurve::drawSpline (QPainter \* painter, const QwtDiMap & xMap, const QwtDiMap & yMap)` [protected]`

Draw a spline.

**Parameters:**

*painter* Painter \
 *xMap* x map \
 *yMap* y map

**See also:**

**QwtCurve::draw**, **QwtCurve::drawCurve**, **QwtCurve::drawDots**, **QwtCurve::drawLines**, **QwtCurve::drawSteps**, **QwtCurve::drawSticks**

Definition at line 583 of file qwt\_curve.cpp.

References closePolyline(), dataSize(), drawLines(), QwtPainter::drawPolygon(), QwtPainter::drawPolyline(), qwtSqr(), QwtSpline::recalc(), QwtSpline::value(), x(), QwtDiMap::xTransform(), and y().

Referenced by drawCurve().

### void QwtCurve::drawSteps (QPainter \* painter, const QwtDiMap & xMap, const QwtDiMap & yMap, int from, int to)` [protected]`

Draw step function.

**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:**

**QwtCurve::draw**, **QwtCurve::drawCurve**, **QwtCurve::drawDots**, **QwtCurve::drawLines**, **QwtCurve::drawSpline**, **QwtCurve::drawSticks**

Definition at line 539 of file qwt\_curve.cpp.

References closePolyline(), QwtPainter::drawPolygon(), QwtPainter::drawPolyline(), QwtDiMap::transform(), x(), and y().

Referenced by drawCurve().

### void QwtCurve::drawSticks (QPainter \* painter, const QwtDiMap & xMap, const QwtDiMap & yMap, int from, int to)` [protected]`

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:**

**QwtCurve::draw**, **QwtCurve::drawCurve**, **QwtCurve::drawDots**, **QwtCurve::drawLines**, **QwtCurve::drawSpline**, **QwtCurve::drawSteps**

Definition at line 473 of file qwt\_curve.cpp.

References QwtPainter::drawLine(), QwtDiMap::transform(), x(), and y().

Referenced by drawCurve().

### void QwtCurve::drawSymbols (QPainter \* painter, QwtSymbol & symbol, const QwtDiMap & xMap, const QwtDiMap & yMap, int from, int to)` [protected, virtual]`

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

Definition at line 865 of file qwt\_curve.cpp.

References QwtSymbol::brush(), QwtSymbol::draw(), QwtSymbol::pen(), QwtSymbol::size(), QwtDiMap::transform(), x(), and y().

Referenced by draw().

### void QwtCurve::init (const QString & title)` [protected]`

Initialize data members.

Definition at line 22 of file qwt\_curve.cpp.

Referenced by QwtCurve().

### double QwtCurve::maxXValue () const

**boundingRect()**.x2()

Definition at line 113 of file qwt\_curve.h.

### double QwtCurve::maxYValue () const

**boundingRect()**.y2()

Definition at line 117 of file qwt\_curve.h.

### double QwtCurve::minXValue () const

**boundingRect()**.x1()

Definition at line 111 of file qwt\_curve.h.

### double QwtCurve::minYValue () const

**boundingRect()**.y1()

Definition at line 115 of file qwt\_curve.h.

### const QwtCurve & QwtCurve::operator= (const QwtCurve & c)

Copy Assignment.

Definition at line 69 of file qwt\_curve.cpp.

References copy(), and curveChanged().

Referenced by QwtPlotCurve::operator=().

### int QwtCurve::options () const

Return the current style options.

**See also:**

**QwtCurve::setOptions**

Definition at line 795 of file qwt\_curve.cpp.

Referenced by QwtPlot::curveOptions().

### const QPen & QwtCurve::pen () const

Return the pen used to draw the lines.

**See also:**

**QwtCurve::setPen**

Definition at line 165 of file qwt\_curve.cpp.

Referenced by QwtPlotPrintFilter::apply(), QwtPlot::curvePen(), QwtPlotPrintFilter::reset(), and QwtPlot::updateLegendItem().

### void QwtCurve::setBaseline (double ref)

Set the value of the baseline.

The baseline is needed for filling the curve with a brush or the QwtCurve::Sticks drawing style. The default value is 0.0. The interpretation of the baseline depends on the style options. With QwtCurve::Yfx, the baseline is interpreted as a horizontal line at y = **baseline()**, with QwtCurve::Yfy, it is interpreted as a vertical line at x = **baseline()**.

**Parameters:**

*ref* baseline

**See also:**

**QwtCurve::setBrush()**, **QwtCurve::setStyle()**, **QwtCurve::setOptions()**

Definition at line 897 of file qwt\_curve.cpp.

References curveChanged().

Referenced by QwtPlot::setCurveBaseline().

### void QwtCurve::setBrush (const QBrush & brush)

Assign a brush. In case of brush.style() != QBrush::NoBrush and **style()** != QwtCurve::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:**

**QwtCurve::brush**, **QwtCurve::setBaseline**, **QwtCurve::baseline**

Definition at line 182 of file qwt\_curve.cpp.

References curveChanged().

Referenced by QwtPlot::setCurveBrush().

### void QwtCurve::setData (const QwtData & data)

Initialize data with a pointer to **QwtData**.

**Parameters:**

*data* Data

**See also:**

**QwtData::copy**.

Definition at line 257 of file qwt\_curve.cpp.

References QwtData::copy(), and curveChanged().

### void QwtCurve::setData (const QwtArray\< QwtDoublePoint \> & data)

Initialize data with an array of points (explicitly shared).

**Parameters:**

*data* Data

**See also:**

QwtDoublePointData::setData.

Definition at line 243 of file qwt\_curve.cpp.

References curveChanged().

### void QwtCurve::setData (const QwtArray\< double \> & xData, const QwtArray\< double \> & yData)

Initialize data with x- and y-arrays (explicitly shared).

**Parameters:**

*xData* x data \
 *yData* y data

**See also:**

QwtData::setData.

Definition at line 228 of file qwt\_curve.cpp.

References curveChanged().

### void QwtCurve::setData (const double \* xData, const double \* yData, int size)

Set data by copying x- and y-values from specified memory blocks Contrary to **QwtPlot::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**

**See also:**

**QwData::setData.**

**Definition at line 213 of file qwt\_curve.cpp.**

**References curveChanged().**

**Referenced by QwtPlot::setCurveData().**

### void QwtCurve::setOptions (int opt)

**Specify options for the drawing style.**

**The options can be used to modify the drawing style. Options can be or-combined. The following options are defined:**

- **QwtCurve::Auto**

  **The default setting. For QwtCurve::spline, this means that the type of the spline is determined automatically, depending on the data. For all other styles, this means that y is regarded as a function of x.**

- **QwtCurve::Yfx**

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

- **QwtCurve::Xfy**

  **Draws x as a function of y. The baseline is interpreted as a vertical line with x = baseline().**

- **QwtCurve::Parametric**

  **For QwtCurve::Spline only. Draws a parametric spline.**

- **QwtCurve::Periodic**

  **For QwtCurve::Spline only. Draws a periodic spline.**

- **QwtCurve::Inverted**

  **For QwtCurve::Steps only. Draws a step function from the right to the left.**

**Parameters:**

*opt* **new options /sa QwtCurve::options()**

**Definition at line 785 of file qwt\_curve.cpp.**

**References curveChanged().**

**Referenced by QwtPlot::setCurveOptions().**

### void QwtCurve::setPen (const QPen & p)

**Assign a pen.**

**Parameters:**

*p* **New pen**

**Definition at line 152 of file qwt\_curve.cpp.**

**References curveChanged().**

**Referenced by QwtPlotPrintFilter::apply(), QwtPlotPrintFilter::reset(), and QwtPlot::setCurvePen().**

### void QwtCurve::setRawData (const double \* xData, const double \* yData, int size)

**Initialize the data by pointing to memory blocks which are not managed by QwtCurve.**

**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**

**See also:**

**QwtCPointerData::setData.**

**Definition at line 277 of file qwt\_curve.cpp.**

**References curveChanged().**

**Referenced by QwtPlot::setCurveRawData().**

### void QwtCurve::setSplineSize (int s)

**Change the number of interpolated points.**

**Parameters:**

*s* **new size**

**Warning:**

**The default is 250 points.**

**Definition at line 805 of file qwt\_curve.cpp.**

**References curveChanged().**

**Referenced by QwtPlot::setCurveSplineSize().**

### void QwtCurve::setStyle (int style, int options = `0`)

**Set the curve's drawing style.**

**Valid styles are:**

- **QwtCurve::NoCurve**

  **Don't draw a curve. Note: This doesn't affect the symbol.**

- **QwtCurve::Lines**

  **Connect the points with straight lines.**

- **QwtCurve::Sticks**

  **Draw vertical sticks from a baseline which is defined by setBaseline().**

- **QwtCurve::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' option.**

- **QwtCurves::Dots**

  **Draw dots at the locations of the data points. Note: This is different from a dotted line (see setPen()).**

- **QwtCurve::Spline**

  **Interpolate the points with a spline. The spline type can be specified with setOptions(), the size of the spline (= number of interpolated points) can be specified with setSplineSize().**

- **QwtCurve::UserCurve ...**

  **Styles \>= QwtCurve::UserCurve are reserved for derived classes of QwtCurve that overload QwtCurve::draw() with additional application specific curve types.**

**See also:**

**QwtCurve::style()**

**Definition at line 110 of file qwt\_curve.cpp.**

**References curveChanged().**

**Referenced by QwtPlot::setCurveStyle().**

### void QwtCurve::setSymbol (const QwtSymbol & s)

**Assign a symbol.**

**Parameters:**

*s* **symbol**

**See also:**

**QwtSymbol**

**Definition at line 132 of file qwt\_curve.cpp.**

**References curveChanged().**

**Referenced by QwtPlotPrintFilter::apply(), QwtPlotPrintFilter::reset(), and QwtPlot::setCurveSymbol().**

### void QwtCurve::setTitle (const QString & title)

**Assign a title to a curve.**

**Parameters:**

*title* **new title**

**Definition at line 288 of file qwt\_curve.cpp.**

**References curveChanged().**

**Referenced by QwtPlot::insertCurve(), and QwtPlot::setCurveTitle().**

### int QwtCurve::splineSize () const

**Return the spline size.**

**See also:**

**QwtCurve::setSplineSize**

**Definition at line 817 of file qwt\_curve.cpp.**

**Referenced by QwtPlot::curveSplineSize().**

### int QwtCurve::style () const

**Return the current style.**

**See also:**

**QwtCurve::setStyle**

**Definition at line 122 of file qwt\_curve.cpp.**

**Referenced by QwtPlot::curveStyle(), and QwtPlot::updateLegendItem().**

### const QwtSymbol & QwtCurve::symbol () const

**Return the current symbol.**

**See also:**

**QwtCurve::setSymbol**

**Definition at line 142 of file qwt\_curve.cpp.**

**Referenced by QwtPlotPrintFilter::apply(), QwtPlot::curveSymbol(), QwtPlotPrintFilter::reset(), and QwtPlot::updateLegendItem().**

### const QString & QwtCurve::title () const

**Return the title.**

**See also:**

**QwtCurve::setTitle**

**Definition at line 298 of file qwt\_curve.cpp.**

**Referenced by QwtPlot::curveTitle(), and QwtPlot::updateLegendItem().**

### int QwtCurve::verifyRange (int & i1, int & i2)` [protected]`

**Checks if a range of indices is valid and corrects it if necessary.**

**Parameters:**

*i1* **Index 1** \
 *i2* **Index 2**

**Definition at line 331 of file qwt\_curve.cpp.**

**References dataSize(), qwtLim(), and qwtSort().**

**Referenced by draw().**

### double QwtCurve::x (int i) const

**Parameters:**

*i* **index**

**Returns:**

**x-value at position i**

**Definition at line 205 of file qwt\_curve.h.**

**Referenced by QwtPlot::closestCurve(), drawDots(), drawLines(), drawSpline(), drawSteps(), drawSticks(), and drawSymbols().**

### double QwtCurve::y (int i) const

**Parameters:**

*i* **index**

**Returns:**

**y-value at position i**

**Definition at line 214 of file qwt\_curve.h.**

**References QwtData::y().**

**Referenced by QwtPlot::closestCurve(), drawDots(), drawLines(), drawSpline(), drawSteps(), drawSticks(), and drawSymbols().**

## Author

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