Qt - How to define axis intervals on QCustomPlot?

Question

I'm using QCustomPlot , on Qt, to plot aspects of a video sequence.

I would like to define the background of my graph in order to define specific zones along my yAxis . My graph is this:

And i would like to define intervals in my yAxis to get something like this:

The last image belongs to a program called PEAT, used to analyse videos that can trigger epilepsy seizures. I am pointing to the way that they define the zones along the yAxis .

Any suggestions?

Answer 1

To have a region in the plot, you can add two graphs which define the bounds of the region :

  //Upper bound
  customPlot->addGraph();
  QPen pen;
  pen.setStyle(Qt::DotLine);
  pen.setWidth(1);
  pen.setColor(QColor(180,180,180));
  customPlot->graph(0)->setName("Pass Band");
  customPlot->graph(0)->setPen(pen);
  customPlot->graph(0)->setBrush(QBrush(QColor(255,50,30,20)));

  //Lower bound
  customPlot->addGraph();
  customPlot->legend->removeItem(customPlot->legend->itemCount()-1); // don't show two     Band graphs in legend
  customPlot->graph(1)->setPen(pen);

Next you can fill the area between the bounds using setChannelFillGraph :

  customPlot->graph(0)->setChannelFillGraph(customPlot->graph(1));

Also don't forget to assign the relevant values for the bounds :

  QVector<double> x(250);
  QVector<double> y0(250), y1(250);

  for (int i=0; i<250; ++i)
  {
      x[i] = i ;
      y0[i] = upperValue;

      y1[i] = lowerValue;

  }
  customPlot->graph(0)->setData(x, y0);
  customPlot->graph(1)->setData(x, y1);

You can also add other graphs to show some boundaries like the one in your example.