cannot see the curve, after attaching it to Plot

Hello,

I have created a qwtPlotCurve and attached it to a QwtPlot, but I cannot see any curve there. Please help me to get it visible.

In this function I create the curves:

Code:

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void OscillationGRN::plotCurves(){
 
	for(int j = 0; j < ListOfPlots.size(); ++j){
			//create new Curve
		QwtPlotCurve *newCurve = new QwtPlotCurve();
		newCurve->setPen(QColor(Qt::red));
		newCurve->setStyle(QwtPlotCurve::Lines);
		newCurve->setCurveAttribute(QwtPlotCurve::Fitted);
 
		double range[] ={0,20};
		double step = 0.1;
		// copy the data into the curves
			newCurve->setData(CurveData(range, step));
		newCurve->attach(ListOfPlots[j]);
 
	}
}

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whereby

Code:

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QVector<QwtPlot*> ListOfPlots;

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is and CurveData is a class inherited from QwtData:

Code:

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class CurveData: public QwtData
{
    // The x values depend on its index and the y values
    // can be calculated from the corresponding x value.
    // So we don't need to store the values.
    // Such an implementation is slower because every point
    // has to be recalculated for every replot, but it demonstrates how
    // QwtData can be used.
 
public:
	CurveData( double rang1[2], double step)
    {
    	rangeX[0]= rang1[0];	rangeX[1] = rang1[1];
    	range = (rangeX[1] - rangeX[0])/step;
    	if(range<0){
    		range = range *(-1);
    	}
    	d_size = size_t(range);
    	cout << "range = "<< range << " , d_size= " << d_size<< endl;    // <<<<<<<< this output IS seen in console
    }
 
    virtual QwtData *copy() const
    {
        return new CurveData(*this);
    }
 
    virtual size_t size() const
    {
        return d_size;
    }
 
    virtual double x(size_t i) const
    {
    	cout << "x = " << rangeX[0] + i*((rangeX[1]- rangeX[0])/range) << endl;   // <<<<<<<< this output is NOT seen in console
    	// here the array with x values will be produced
    	return rangeX[0] + i*((rangeX[1]- rangeX[0])/range);
    }
 
    virtual double y(size_t i) const
    {
    	cout << "y = " << sin(2*3.1415926*x(i)/T)+1.0 << endl;   // <<<<<<<< this output is NOT seen in console
    	return sin(2*3.1415926*x(i)/T)+1.0;
    }
private:
    size_t d_size;
    double range;
   double rangeX[2];
 
};

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by the way, if I generate x and y data by myself, it does not work, too.

Code:

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void OscillationGRN::plotCurves(){
 
	for(int j = 0; j < ListOfPlots.size(); ++j){
			//create new Curve
		QwtPlotCurve *newCurve = new QwtPlotCurve();
		newCurve->setPen(QColor(Qt::red));
		newCurve->setStyle(QwtPlotCurve::Lines);
		newCurve->setCurveAttribute(QwtPlotCurve::Fitted);
		const unsigned Size=200;
		double xval[Size];
		double yval[Size];
		double ti=0;
			for(unsigned i=0; i<Size; ++i){
				xval[i] = ti;
			  yval[i] = sin(2*3.1415926*ti/T)+1.0;
			  ti= ti+0.1;
			}
 
			newCurve->setRawData(xval,yval, Size);
		newCurve->attach(ListOfPlots[j]);
 
	}
}

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I'm sorry for the previous posts. I have made a big mistake forgeting to call "replot()"! :)

Code:

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ListOfPlots[j]->replot();

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