QChart Multiple Lines with QString as X Axis instead of double values



  • Hi Guys,

    I want to create a chart with Dates as X Axis instead of values.
    I tried it with category like in this example http://doc.qt.io/qt-5/qtcharts-lineandbar-example.html but the problem is that the Q String arent on the exact Position where the Point of the line is ... because it is for bar charts...
    I hope that sb has an idea.

    This is my code :

                Buger->createDefaultAxes();
                Buger->axisX()->setTitleText("Time Step");
                QStringList categories;
                categories << "Jan" << "Feb" << "Mar" << "Apr" << "May" << "Jun";
                QBarCategoryAxis *axisX = new QBarCategoryAxis();
                axisX->append(categories);
                Buger->setAxisX(axisX);
                Buger->axisY()->setTitleText("Speed [km/s]");
                
    

    Thanks in advance !



  • @BadHombre

    I want to create a chart with Dates as X Axis instead of values

    Then instead of QBarCategoryAxis what about QDateTimeAxis (https://doc.qt.io/qt-5/qdatetimeaxis.html)?



  • Thanks for the Solution ... but i have one additional question :

    i created now chart with the QDateTime example ...
    my Problem now is that it takes random date time values for the x axis ... but i want that it takes exactly the datetimes which i added to the series...

    any idea ?

     QDateTimeAxis *axisX = new QDateTimeAxis;
                            //axisX->setTickCount(AllStepDatesAsQDatetime.size());
                            axisX->setFormat("MMM:dd:yyyy - hh:dd");
                            axisX->setTitleText("Date");
                            axisX->
                            Buger->addAxis(axisX, Qt::AlignBottom);
                            bugerseries1->attachAxis(axisX);
    


  • @BadHombre
    As you can see from the docs of QDateTimeAxis, it has a (settable) number of "ticks", which I imagine correspond to (regulary-spaced) labels, and you cannot make it only produce ticks where you have plotted points. I don't know whether you can override its axis stuff and do your own.

    If you revert to QBarCategoryAxis, I don't know exactly where it places the label text anyway, but in any case everything will be regularly-spaced, which then won't correspond to the actual "gap" between dates.

    So far as I can see, all the axis-types work by regularly-spaced ticks, I don't think you can alter that or control exactly where the tick/label is placed. Unless, that is, an expert know better....


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