code: def setPoint(self, x, group, y):
          
          if x == -1:
              # silence window
              self.plot([0],[y], symbol='o')
          else:
              yindex = self.groups.index(group)
              xdata, ydata = self.lines[yindex].getData()
              if ydata is None:
                  xdata = [x]
                  ydata = [y]
              else:
                  xdata = np.append(xdata, x)
                  ydata = np.append(ydata, y)
              self.lines[yindex].setData(xdata, ydata)
docs: Sets the given point, connects line to previous point in group
  
          :param x: x value of point
          :type x: float
          :param group: group which plot point for
          :type group: float
          :param y: y value of point
          :type y: float