Auto scale, but no plot data

[pdm]

Hi all,

This is my first time posting, and my first time trying to use Qwt. I am presently working on Win7 with Qt 5.5.1, and Qwt 6.1.2. I am compiling with VS2013 32. Everything seems to be installed properly, and I am using creator with the Qwt plugin.

I haven't found a lot of examples, but pieced a test program together with what I found and the Qwt documentation.

Current issue...
My program compiles and runs with no warnings.
When I call (update plot), the plot will auto scale the axis to my data but the plot doesn't show any data. It is completely blank.

I have a feeling it is something I am overlooking, or don't know about.
I am stuck and would appreciate any pointers.

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    ui->qwtPlot->setTitle("Plot 1");
    ui->qwtPlot->setAxisTitle(QwtPlot::xBottom, "X axis");
    ui->qwtPlot->setAxisTitle(QwtPlot::yLeft, "Y axis");
    ui->qwtPlot->setCanvasBackground(Qt::white);
 
    QwtPlotCurve testCurve("Test Curve");
 
    QVector<double> x;
    QVector<double> y;
 
    for(int i = 0; i<500; i++)
    {
        x.push_back(i);
        y.push_back(i*i);
    }
 
    testCurve.setSamples(x, y);
    //testCurve.setRawSamples(x.data(), y.data(), y.size());
 
    myCurve.setPen(QPen(Qt::red));
 
    testCurve.attach(ui->qwtPlot);
 
    ui->qwtPlot->replot();
    //ui->qwtPlot->show();
 
}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    ui->qwtPlot->setTitle("Plot 1");
    ui->qwtPlot->setAxisTitle(QwtPlot::xBottom, "X axis");
    ui->qwtPlot->setAxisTitle(QwtPlot::yLeft, "Y axis");
    ui->qwtPlot->setCanvasBackground(Qt::white);

    QwtPlotCurve testCurve("Test Curve");

    QVector<double> x;
    QVector<double> y;

    for(int i = 0; i<500; i++)
    {
        x.push_back(i);
        y.push_back(i*i);
    }

    testCurve.setSamples(x, y);
    //testCurve.setRawSamples(x.data(), y.data(), y.size());

    myCurve.setPen(QPen(Qt::red));

    testCurve.attach(ui->qwtPlot);

    ui->qwtPlot->replot();
    //ui->qwtPlot->show();
    
}

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Also, I just set up another computer exactly the same as previously described, but with VS2010. Same results.

Thanks

[Uwe]

testCurve is on the stack and therefore gone, when you leave the constructor of MainWindow.
Concerning examples: there are several in the official tarball.

Uwe

[pdm]

Uwe,

I knew it was something I was overlooking. My plot looks great now.

Thanks for the excellent library, and the assistance.