def add_coord(self, x, y):
        """ Adds a coord to the polyline and creates another circle
        """
        x = x*self.x_factor
        y = y*self.y_factor
        self.plotData.add_coord(x, y)
        self.circles_list.append(gui.SvgCircle(x, y, self.circle_radius))
        self.append(self.circles_list[-1])
        if len(self.circles_list) > self.maxlen:
            self.remove_child(self.circles_list[0])
            del self.circles_list[0]
Adds a coord to the polyline and creates another circle