how to prevent scatter handle deletion!

Question

john_arle 2019-10-26

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https://ww2.mathworks.cn/matlabcentral/answers/487544-how-to-prevent-scatter-handle-deletion

回答： john_arle 2019-10-26

采纳的回答： john_arle

在 MATLAB Online 中打开

Hello!

In a for loop, I first initialize a scatter plot, and then I update it.

However, when adding a second handle (lines_handle) to my code,

the former (scatter_handle) tells me that the object scatter has been deleted.

It is probably because I am assigning another scatter plot to lines_handle.

I believe this should not happen and most of all I do not know how to prevent it.

Thank you.

You can see my code below, look at the only comment to see where the scatter object is deleted!

                if self.plot_initialized == 0 
                    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]');
                    axis square;
                    view(0,90);
                    grid 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, ...
                        'Zdata', -pd, 'Marker', '.', 'SizeData', ...
                        size_agents, 'CData', colours');
                    colour = 200*ones(10, 3);
                    for agent = 1:swarm.nb_drones
                        self.scatter_handle
                        agent
     
                        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);
                        % Here it is where scatter_handle gets deleted!
                        self.scatter_handle
                    end
                    drawnow;
                end
                title(sprintf('Simulation time: %.2f seconds', time));

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john_arle 2019-10-26

编辑：john_arle 2019-10-26

在 MATLAB Online 中打开

I had to add hold on instruction after the first scatter instruction. Otherwise, Matlab next scatter deletes the previous one no matter what.

Thank you, John!

                        if self.plot_initialized == 0 
                    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]');
                    axis square;
                    view(0,90);
                    grid on;
                    hold on;    % HERE IT IS WHERE I INSERTED A  HOLD ON LINE!
                    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, ...
                        'Zdata', -pd, 'Marker', '.', 'SizeData', ...
                        size_agents, 'CData', colours');
                    colour = 200*ones(10, 3);
                    for agent = 1:swarm.nb_drones
                        self.scatter_handle
                        agent
     
                        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);
                        % Here it is where scatter_handle gets deleted!
                        self.scatter_handle
                    end
                    drawnow;
                end
                title(sprintf('Simulation time: %.2f seconds', time));