Plot x^2 curve

Hi all,

I have this code to plot the x^2 curve:

Code:

---

// add curves
    QwtPlotCurve *curve1 = new QwtPlotCurve("Graph 1");
 
    //set curve color
    curve1->setPen(QPen(Qt::red, 2));
 
    // add curves
    curve1->attach(ui->qwtPlotWidget);
 
    const int MAX_VALUES = 100;
    double x[2*MAX_VALUES], y1[2*MAX_VALUES];// x and y values
    for (int i (-MAX_VALUES); i < MAX_VALUES; i++)
    {
        x[i] = i;
        y1[i] = i*i;
    }
 
    // copy the data into the curves
    curve1->setSamples(x, y1, 2*MAX_VALUES);
 
    // finally, refresh the plot
    ui->qwtPlotWidget->replot();

---

But I get this strange plot:

http://i48.tinypic.com/2drw5lx.jpg

What's wrong?

Regards.

You are definitely missing "=" in line #12. x[-100..-1] and y[-100..-1] likely point to some garbage as well.

Can you put the right code please?

Regards.

Code:

---

for(int i=0;i<MAX_VALUES*2;++i) {
  x[i] = -MAX_VALUES+i;
  y1[i] = x[i]*x[i];
}

---

Thank you!