Read contents of QwtSeriesData<QPointF>

[cstr]

Hi all,

QwtSeriesData<QPointF>* coordinates = new FunctionData(::sin);

QwtSeriesData<QPointF>* coordinates = new FunctionData(::sin);

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Considering the line above, I have a question on how to read the values from the QwtSeriesData<QPointF> object. The code I am dealing with accept both constructions below, but the second one is preferable.

MyPlotCurve *sinCurve = guiComVisGraf->createCurve("Seno", coordinates );
MyPlotCurve *sinCurve = guiComVisGraf->createCurve("Seno", size, x, y);

MyPlotCurve *sinCurve = guiComVisGraf->createCurve("Seno", coordinates );
MyPlotCurve *sinCurve = guiComVisGraf->createCurve("Seno", size, x, y);

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So I am trying this

int size = coordinates->size();
double *x = new double[size];
double *y = new double[size];
for(int i = 0; i < size; i++){
    x[i] = coordinates->sample(i).x();
    y[i] = coordinates->sample(i).y();
}
MyPlotCurve *sinCurve = guiComVisGraf->createCurve("Seno", size, x, y);

int size = coordinates->size();
double *x = new double[size];
double *y = new double[size];
for(int i = 0; i < size; i++){
    x[i] = coordinates->sample(i).x();
    y[i] = coordinates->sample(i).y();
}
MyPlotCurve *sinCurve = guiComVisGraf->createCurve("Seno", size, x, y);

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This way I am reading "0" for all "i". There is probably a neat misunderstanding in my code, I would like to ask for help in find it. Thanks in advance.

[Uwe]

Assuming that FunctionData is taken from the sinusplot example the code above doesn't make much sense - together with the rest of your question.

Better take this code for learning the very basics of how to show a curve on a QwtPlot: http://qwt.svn.sourceforge.net/viewv...75&view=markup.

Uwe

int main( int argc, char **argv )
{
 	QApplication a( argc, argv );
 
	QwtPlot plot;
 	plot.setTitle( "Plot Demo" );
 	plot.setCanvasBackground( Qt::white );
 	plot.setAxisScale( QwtPlot::yLeft, 0.0, 10.0 );
 	plot.insertLegend( new QwtLegend() );
 
 	QwtPlotGrid *grid = new QwtPlotGrid();
 	grid->attach( &plot );
 
 	QwtPlotCurve *curve = new QwtPlotCurve();
 	curve->setTitle( "Some Points" );
 	curve->setPen( QPen( Qt::blue, 4 ) ),
 	curve->setRenderHint( QwtPlotItem::RenderAntialiased, true );
 
 	QwtSymbol *symbol = new QwtSymbol( QwtSymbol::Ellipse,
 	QBrush( Qt::yellow ), QPen( Qt::red, 2 ), QSize( 8, 8 ) );
 	curve->setSymbol( symbol );
 
 	QPolygonF points;
 	points << QPointF( 0.0, 4.4 ) << QPointF( 1.0, 3.0 )
 	    << QPointF( 2.0, 4.5 ) << QPointF( 3.0, 6.8 )
 	    << QPointF( 4.0, 7.9 ) << QPointF( 5.0, 7.1 );
 	curve->setSamples( points );
 
 	curve->attach( &plot );
 
 	plot.resize( 600, 400 );
 	plot.show();
 
 	return a.exec();
 }

int main( int argc, char **argv )
{
 	QApplication a( argc, argv );
	
	QwtPlot plot;
 	plot.setTitle( "Plot Demo" );
 	plot.setCanvasBackground( Qt::white );
 	plot.setAxisScale( QwtPlot::yLeft, 0.0, 10.0 );
 	plot.insertLegend( new QwtLegend() );
 	
 	QwtPlotGrid *grid = new QwtPlotGrid();
 	grid->attach( &plot );
 	
 	QwtPlotCurve *curve = new QwtPlotCurve();
 	curve->setTitle( "Some Points" );
 	curve->setPen( QPen( Qt::blue, 4 ) ),
 	curve->setRenderHint( QwtPlotItem::RenderAntialiased, true );
 	
 	QwtSymbol *symbol = new QwtSymbol( QwtSymbol::Ellipse,
 	QBrush( Qt::yellow ), QPen( Qt::red, 2 ), QSize( 8, 8 ) );
 	curve->setSymbol( symbol );
 	
 	QPolygonF points;
 	points << QPointF( 0.0, 4.4 ) << QPointF( 1.0, 3.0 )
 	    << QPointF( 2.0, 4.5 ) << QPointF( 3.0, 6.8 )
 	    << QPointF( 4.0, 7.9 ) << QPointF( 5.0, 7.1 );
 	curve->setSamples( points );
 	
 	curve->attach( &plot );
 	
 	plot.resize( 600, 400 );
 	plot.show();
 	
 	return a.exec();
 }

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[cstr]

May be the problem was not clearly stated. I was not reading the values corresponding to the sinus curve inside coordinates. For some reason it seems that the data become available in coordinates only after a replot. May be some one can discuss what happens behind the scenes...

For me it was sufficient to do this:

double *xSin = new double[size];
double *ySin = new double[size];
for(int i = 0; i < size; i++){  /* Gera pontos do seno. */
    xSin[i] = i;
    ySin[i] = ::sin(i);
}

double *xSin = new double[size];
double *ySin = new double[size];
for(int i = 0; i < size; i++){  /* Gera pontos do seno. */
    xSin[i] = i;
    ySin[i] = ::sin(i);
}

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