Scatter doen not plot!

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john_arle 2019-10-27

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Hello!

The code lines written below are inserted in a for loop. Depending on whether

my figure has been initialized or not, the former or the latter part of the code is

executed. However, after the first iteriation (where the figure is initialized),

points disappear from the figure and do not come back.

As you can see, I used the instruction drawnow, but it seems useless.

I hope someone of you guys knows how to solve my issue!

Best,

John_Arlecchino.

 if self.plot_initialized == 0 % Initializing figure
                    self.figure_handle = figure; clf;
                    grid on;
                    colours = swarm.get_colors();
                    size_agents = repmat(30, swarm.nb_drones, 1); 
                    pn = x_current(1, :);
                    pe = x_current(2, :);
                    pd = x_current(3, :);
                    self.scatter_handle = scatter3(pe, pn, -pd, size_agents, colours', 'filled');
                    for agent = 1:swarm.nb_drones
                        self.wake = zeros(10, 3, swarm.nb_drones);
                        for i = 1:10
                            self.wake(i, 1:3, agent) = x_current(1:3, agent);
                        end
                    end
                    
                    xlabel('Y position [m]');
                    ylabel('X position [m]');
                    zlabel('Z position [m]');
                    xlim([-200 300])
                    ylim([-200 300])
                    axis square;
                    view(0,90);
                    grid on;
                    hold on;
                    self.plot_initialized = 1;
                    %----------------------------------------------------------
                else 
                    size_agents = repmat(30, swarm.nb_drones, 1);
                    colours = swarm.get_colors();
                    pn = x_current(1, :);
                    pe = x_current(2, :);
                    pd = x_current(3, :);
                    set(self.scatter_handle, 'Xdata', pe, 'Ydata', pn, ...        % Here it is where points on plot disappear!
                        'Zdata', -pd, 'Marker', '.', 'SizeData', ...
                        size_agents, 'CData', colours');
                    xlabel('Y position [m]');
                    ylabel('X position [m]');
                    zlabel('Z position [m]');
                    axis square;
                    view(0,90);
                    grid on;
                    hold on;
                    colour_wake = 200*ones(10, 3); 
                    for agent = 1:swarm.nb_drones
                        self.wake = circshift(self.wake, 1);
                        self.wake(1, :, agent) = x_current(:, agent);
                        self.lines_handle(agent) = scatter(...
                            self.wake(1:end, 2, agent), ...
                            self.wake(1:end, 1, agent), 4, colour_wake);
                        hold on;
                        drawnow;
                    end
                end

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Rik 2019-10-27

Your setting hold on after you created a new plot with the scatter function. You also aren't using any explicit parent when creating your graphical elements. This is probably fine in the initialization phase (as the user probably wouldn't select another figure during that part), but especially in the second part of your code, this is required for a robust GUI design.

The drawnow function forces a graphics update (and the execution of any queued callbacks), so that can be helpful if you want to show the user something changing in a loop, but it does not actually create new graphical elements.

I hope this helps.

john_arle 2019-10-27