QCustomPlot how to addData

[MScottM]

Hello again!

I'm having trouble with the following code:

void MainWindow::graphSelected(QStringList _graphingData) {
    QList<QStringList> list;
    QList<double> data;
    foreach (const QString &s, _graphingData) {
        const QStringList parts = s.split(",");
        list.append(parts);
        Q_ASSERT(parts.size() >= 3);
        data.append(parts.at(2).toDouble());
    }

    QVector<double> y = QVector<double>::fromList(data);

    if (Debug) {
    qDebug() << list;
    qDebug() << data;
    }

    int j = data.size();
    QVector<double> x[j];

    for (int i=0; i<j; i++) {
        x[i]<<i;
    }
    customPlot->addGraph();
    customPlot->graph(0)->addData(x, y);  // <- error "no matching function for call to 'QCPGraph::addData(QVector<double> [j], QVector<double>&)'
    customPlot->graph(0)->addData(x, y);
    customPlot->xAxis->setLabel("x - time");
    customPlot->yAxis->setLabel("y - value");
    customPlot->graph(0)->rescaleAxes();
    customPlot->replot();
}

My understanding is that addData is supposed to take (QVector<T>, QVector<T>). I've spent hours trying to solve this - different data types, different ways of calling it (->setData...), with no luck, so I'm asking for help (again).

Thanks.

[Paul Colby]

Hi @MScottM,

The problem, I suspect, is this line:

QVector<double> x[j];

Here you have an array of j vectors of 0 doubles each.

Instead, do something like:

QVector<double> x(j);

Which gives a single vector of j doubles.

Cheers.

[MScottM]

Once again @Paul-Colby, that did the trick! That and changing x[i]<<i; back to x[i]=i; I knew it was some kind of rookie mistake.

It seems to be plotting now, but instead of putting the data on the QWidget that I promoted to a QCustomPlot, it is squishing it up in the corner of my main window...

Have you or anyone seen this behavior, or I could take this to the QCustomPlot support forum...?

Thanks again for putting me on the right track!

[mrjj]

Hi
Are you sure that is the promoted one ?
From code you say
customPlot->xxxx
for a promoted its normally
ui->customPlot->xxxx

It seems more like one you NEW and not assign to a layout.

[MScottM]

Aha! That was it @mrjj. In my MainWindow setup I had: ui->customPlot = new QCustomPlot(this); I probably put it in there while following some tutorial or other on QCustomPlot.

Solved!