Hello!

I would like dynamically rewrite chart, generated by QSplineSeries.
I am trying to achieve it this way:

Qt Code: 
  1. QSplineSeries* series_for_Vy= new QSplineSeries();
  2.      QChart* chart_for_Vy = new QChart();
  3. QGroupBox *Widget::set_splinechart_Vy()
  4. {
  5.  
  6.     int n ; //номер шага по времени
  7.     number_of_step_for_Vy = new QLineEdit("steps");
  8.  
  9.     series_for_Vy->append(3,3);
  10.     series_for_Vy->append(2,5);
  11.  
  12.     chart_for_Vy->legend()->hide();
  13.     chart_for_Vy->addSeries( series_for_Vy);
  14.     chart_for_Vy->setTitle("Vy (N)");
  15.     chart_for_Vy->createDefaultAxes();
  16.     chart_for_Vy->axisY()->setRange(0,  10);
  17.     chart_for_Vy->axisX()->setRange(0,10);
  18.     chart_for_Vy->axisX()->setTitleText("Number of Node, N");
  19.     chart_for_Vy->axisY()->setTitleText("Velocity, Vy");
  20.  
  21.  
  22.  
  23.         QChartView *chartView = new QChartView(chart_for_Vy);
  24.  
  25.  
  26.     slider_for_Vy = new QSlider(Qt::Orientation::Horizontal);
  27.     slider_for_Vy->setRange(1,999);
  28.  
  29.  
  30.     QVBoxLayout *vert = new QVBoxLayout;
  31.     QHBoxLayout *horiz = new QHBoxLayout;
  32.     vert->addWidget(chartView);
  33.    // vert->addWidget(slider);
  34.     horiz->addWidget(slider_for_Vy,Qt::AlignLeft);horiz->addWidget(number_of_step_for_Vy);
  35.     vert->addLayout(horiz);
  36.     QGroupBox* groupbox = new QGroupBox("Y-component of velocity");
  37.     groupbox->setLayout(vert);
  38.     //connect(number_of_step_for_Vy,SIGNAL(textEdited(QString)),SLOT(update()));
  39.     return groupbox;
  40. }
  41.  
  42. void Widget::plot_Velocity_Y()
  43. {
  44.     series_for_Vy->clear();
  45.     series_for_Vy->append(3,3);
  46.     series_for_Vy->append(2,9);
  47.     chart_for_Vy->clearFocus();
  48.     chart_for_Vy->addSeries( series_for_Vy);
  49.  
  50. }
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But when program comes to SLOT plot_Velocity_Y, it does not change and lines appear:
"Can not add series. Series already on the chart."

How to handle this?