qtc++11qt5.7

co-ordinates on x axis are incorrect / auto-adjusted in QT Line Chart

I am creating a simple line chart graph in QT 5.7.

Following is my certificate_page_childs table structure:

enter image description here

My c++ code : 

QLineSeries *series = new QLineSeries();
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
QString db_path = QDir::currentPath();
db_path =  db_path + QString("/some_file");
db.setDatabaseName(db_path);
db.open();
QSqlQuery query;
 query.prepare("SELECT hardness_val FROM certificate_page_childs where cp_id=:value");
 query.bindValue(0,statisticalanalysis::cert_id_gbl);
 if(query.exec()){
      int d = 1;
      while (query.next()) {
          series->append(d, query.value(0).toDouble()); //Method 1
          //qDebug() << query.value(0).toString();
          //*series << QPointF(d,query.value(0).toDouble()); // Method 2
          qDebug() << d;
          d++;

      }
 }
 else
 {
     qDebug() << query.lastError();
 }
 db.close();
 QChart *chart = new QChart();
 chart->legend()->hide();
 chart->addSeries(series);
 chart->createDefaultAxes();
 chart->setTitle("Simple line chart example");
 chart->setAnimationOptions(QChart::SeriesAnimations);
 ui->graphicsView->setRenderHint(QPainter::Antialiasing);
 ui->graphicsView->setChart(chart);

Following is my output :

enter image description here

What i need :

enter image description here

X axis : No of readings

Y axis : Some value per reading

Please compare the x-axis with the output image and the desired one.

Can anyone guide me till desired results are achieved ?

Solution

  • In this particular case as the X axis you have values ​​of 1:1:n you can set a tickCount and the labelFormat:

    QChart *chart = new QChart();
chart->legend()->hide();
chart->addSeries(series);
chart->createDefaultAxes();
chart->setTitle("Simple line chart example");
chart->setAnimationOptions(QChart::SeriesAnimations);
ui->graphicsView->setRenderHint(QPainter::Antialiasing);
ui->graphicsView->setChart(chart);
QValueAxis *axisX = static_cast<QValueAxis *>(chart->axisX(series)); // <--
axisX->setTickCount(series->count());  // <--
axisX->setLabelFormat("%d"); // <--