How to create Subplot using QCharts?

I want to create two subplots (like 2 rows), the first plot will show the line series graph based on Analog to Digital Converter counts stored in a text file and the second plot will show the line series graph based on Temperature values stored in a text file. I am able to plot the line series in the same plot, but I want to plot it in two separate subplots.

#include <QApplication>
#include <QMainWindow>
#include <QFile>
#include <QTextStream>
#include <QDateTime>
#include <QTime>
#include <QtCharts/QChartView>
#include <QtCharts/QLineSeries>
#include <QDateTimeAxis>
#include <QValueAxis>
#include <QDebug>

QT_CHARTS_USE_NAMESPACE

int main(int argc, char *argv[])
{
  QApplication a(argc, argv);

  // Open File
  QFile file("D:\\Projects\\Embedded\\ArduinoTempLogger\\01-21-18.txt");

  if( !file.open(QIODevice::ReadOnly|QIODevice::Text) )
  {
    qDebug() << "File don't exist";
    return  1;
  }
  QTextStream stream(&file);
  QLineSeries *adc_series = new QLineSeries();
  QLineSeries *temp_series = new QLineSeries();
  QDateTime datetime = QDateTime::currentDateTime();
  while( !stream.atEnd() )
  {
    QString line = stream.readLine();
    QStringList values = line.split(",");
    QTime time;
    time = QTime::fromString(values[0], "hh:mm:ss");
    datetime.setTime(time);
    adc_series->append( datetime.toMSecsSinceEpoch(), values[1].toUInt() );
    temp_series->append( datetime.toMSecsSinceEpoch(), values[2].toDouble() );
    // qDebug() << time.toString("hh:mm:ss") << "-->" << datetime.toMSecsSinceEpoch();
  }
  file.close();

  QChart *chart = new QChart();
  chart->legend()->hide();
  chart->addSeries(adc_series);
  chart->addSeries(temp_series);
  // chart->createDefaultAxes();
  chart->setTitle("Temperature Plot");

  // Since we use QLineSeries, calling createDefaultAxes will create QValueAxis both as X and Y axis.
  // To use QDateTimeAxis we need to set it manually to the chart.
  // First, the instance of QDateTimeAxis is created, then the number of ticks to be shown is set.
  //
  QDateTimeAxis *axisX = new QDateTimeAxis;
  axisX->setTickCount(10);
  axisX->setFormat("hh:mm:ss");
  axisX->setTitleText("Time Axis");
  chart->addAxis(axisX, Qt::AlignBottom);
  adc_series->attachAxis(axisX);
  temp_series->attachAxis(axisX);

  QValueAxis *axisY = new QValueAxis;
  axisY->setLabelFormat("%i");
  axisY->setTitleText("Temperature and ADC Value");
  axisY->setRange(0, 100);
  chart->addAxis(axisY, Qt::AlignLeft);
  adc_series->attachAxis(axisY);
  temp_series->attachAxis(axisY);

  QChartView *chartView = new QChartView(chart);
  chartView->setRenderHint(QPainter::Antialiasing);

  QMainWindow window;
  window.setCentralWidget(chartView);
  window.resize(820, 600);
  window.show();

  return a.exec();
}

The data which I am reading from the file is in the following format.

16:08:45,50,24.4
16:08:46,47,22.9
16:08:47,60,29.3
16:08:48,45,22
16:08:49,49,23.9
16:08:50,54,26.4
16:08:51,46,22.5
16:08:52,40,19.5
16:08:53,50,24.4
16:08:54,50,24.4
16:08:55,50,24.4
16:08:56,59,28.8
16:08:57,49,23.9
16:08:58,62,30.3
16:08:59,58,28.3
16:09:00,47,22.9
16:09:01,54,26.4
16:09:02,61,29.8
16:09:03,47,22.9
16:09:04,50,24.4
16:09:05,55,26.9
16:09:06,46,22.5
16:09:07,60,29.3
16:09:08,49,23.9
16:09:09,57,27.8
16:09:10,42,20.5
16:09:11,49,23.9
16:09:12,56,27.3
16:09:13,64,31.3
16:09:14,51,24.9
16:09:15,53,25.9
16:09:16,57,27.8

I am using Qt 5.14.1 on Windows 10 Can someone please guide me achieving in this? Thanks in advance.

Solution

There is no direct solution provided by Qt, so there are several alternatives:

Create 2 QChartView and place them inside a QVBoxLayout.
Create 2 QChart and place them inside a QChartView using a QGraphicsLinearLayout.

The first method is trivial so I will not show an example, however if I show the code of the second method:

#include <QtWidgets>
#include <QtCharts>
QT_CHARTS_USE_NAMESPACE

class GraphicsView: public QGraphicsView{
public:
    GraphicsView(QWidget *parent=nullptr):QGraphicsView(parent){
        setScene(new QGraphicsScene);
        layout = new QGraphicsLinearLayout(Qt::Vertical);
        form = new QGraphicsWidget;
        form->setSizePolicy(QSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding));
        form->setLayout(layout);
        scene()->addItem(form);
        layout->setSpacing(0);
    }
    void addChart(QChart *chart){
        if(chart){
            layout->addItem(chart);
        }
    }
protected:
    void resizeEvent(QResizeEvent *event){
        if(scene())
            scene()->setSceneRect(QRect(QPoint(0, 0), event->size()));
        if(form)
            form->resize(event->size());
        QGraphicsView::resizeEvent(event);
    }
private:
    QGraphicsWidget *form;
    QGraphicsLinearLayout *layout;
};

static bool create_series(QLineSeries *adc_series, QLineSeries *temp_series){
    QFile file("D:\\Projects\\Embedded\\ArduinoTempLogger\\01-21-18.txt");

    if( !file.open(QIODevice::ReadOnly|QIODevice::Text)){
        qDebug() << "File don't exist";
        return false;
    }
    QTextStream stream(&file);
    QDateTime datetime = QDateTime::currentDateTime();
    while( !stream.atEnd()){
        QString line = stream.readLine();
        QStringList values = line.split(",");
        datetime.setTime(QTime::fromString(values[0], "hh:mm:ss"));
        adc_series->append( datetime.toMSecsSinceEpoch(), values[1].toUInt() );
        temp_series->append( datetime.toMSecsSinceEpoch(), values[2].toDouble() );
    }
    file.close();
    return true;
}


static QChart* create_chart(const QString & title, QLineSeries *series){
    QChart * chart = new QChart;
    chart->legend()->hide();
    chart->addSeries(series);

    QDateTimeAxis *axisX = new QDateTimeAxis;
    axisX->setTickCount(10);
    axisX->setFormat("hh:mm:ss");
    axisX->setTitleText("Time Axis");
    chart->addAxis(axisX, Qt::AlignBottom);
    series->attachAxis(axisX);

    QValueAxis *adc_axisY = new QValueAxis;
    adc_axisY->setLabelFormat("%i");
    adc_axisY->setTitleText(title);
    adc_axisY->setRange(0, 100);
    chart->addAxis(adc_axisY, Qt::AlignLeft);
    series->attachAxis(adc_axisY);
    return chart;
}

int main(int argc, char *argv[]){
    QApplication a(argc, argv);

    QLineSeries *adc_series = new QLineSeries;
    QLineSeries *temp_series = new QLineSeries;
    if(!create_series(adc_series, temp_series))
        return -1;

    GraphicsView view;
    view.addChart(create_chart("ADC Value", adc_series));
    view.addChart(create_chart("Temperature Value", temp_series));
    view.show();
    view.resize(640, 480);

    return a.exec();
}

On the other hand, Qt has not given much love to Qt Charts, so simple tasks such as subplots do not exist, so I recommend using other libraries such as QCustomPlot that do offer that functionality, in this link there is an example.