Animated 3D Scatter Plot

Hello,

I would like to create an animated 3D scatter plot that is plotting the points included in the sub-array of a cell DD (102x1 cell), each sub-array is a 29x4 (where the last three column are the 3 coordinates (x,y.z)). Here below an example of my cell and sub-array.

M = [[0;0.2;0.2;0.4;0.6;0.6;0.6],rand(7,3)]
D = diff(find([1;diff(M(:,1));1]));
DD = mat2cell(M,D,4);
DD{:}

The animated scatter should display together each subarray points and then in a subsequent time step the next subarray points.

Here below the code that alreay plot all the points together.

figure(1)
for i = 1:numel(DD)
    hold on; grid on; grid minor; axis equal;
    set(gcf, 'Color', 'White');
    set(gca, 'Fontsize', 12);
    set(gca, 'ZDir','reverse')
    scatter3(DD{i}(:,2),DD{i}(:,3),DD{i}(:,4))
    view(3)
    xlabel('x [mm]')
    ylabel('y [mm]')
    zlabel('z [mm]')
end

Thanks in advance

Answer 1

[Star Strider]

Try this slightly augmented version —

figure(1)
    hold on
    grid minor
    axis([0  2    0  2    0  2])
for i = 1:numel(DD)
    view(3)
    set(gcf, 'Color', 'White');
    set(gca, 'Fontsize', 12);
    set(gca, 'ZDir','reverse')
    scatter3(DD{i}(:,2),DD{i}(:,3),DD{i}(:,4))
    grid on
    axis([0  2    0  2    0  2])
    drawnow
    pause(0.25)
    xlabel('x [mm]')
    ylabel('y [mm]')
    zlabel('z [mm]')
end
hold off

It fixes the axis limits and adds drawnow and pause to create the animation.

Experiment to get the desired results.

.

[Fabio Taccaliti]

Thanks a lot for the answer, the problem is that I would like to have axis equal on my plot but then in order to have it I need the hold on command and this involves that I will plot all the sub-array on top of each other without 'cleaning' the plot each time and plot just one sub-array each time with the 0.25s pause.

Do you know how can I fix it?

[Star Strider]

My pleasure.

When I run the code I posted, the plot does not ‘clear’. All the points are plotted and remain visible, with new ones appearing in each interation of the loop.

Add the axis equal call after the first axis call —

figure(1)
    hold on
    grid minor
    axis([0  2    0  2    0  2])
    axis equal
for i = 1:numel(DD)
    view(3)
    set(gcf, 'Color', 'White');
    set(gca, 'Fontsize', 12);
    set(gca, 'ZDir','reverse')
    scatter3(DD{i}(:,2),DD{i}(:,3),DD{i}(:,4))
    grid on
    axis([0  2    0  2    0  2])
    drawnow
    pause(0.25)
    xlabel('x [mm]')
    ylabel('y [mm]')
    zlabel('z [mm]')
end
hold off

Both of the axis calls are necessary.

.

[Fabio Taccaliti]

Sorry maybe from what I wrote was not clear.

I would like that the plot 'clear' each iteration without showing the one from the previous.

Now from this code the axis remain equal that is perfect, but still all the points are plotted and remain visible (which I would like to avoid ) and show just the point for each iteration.

I tried several combination of hold on and hold off but still nothing.

[Star Strider]

To do that, remove the hold calls —

figure(1)
grid minor
axis([0  2    0  2    0  2])
axis equal
for i = 1:numel(DD)
    view(3)
    set(gcf, 'Color', 'White');
    set(gca, 'Fontsize', 12);
    set(gca, 'ZDir','reverse')
    scatter3(DD{i}(:,2),DD{i}(:,3),DD{i}(:,4), 'filled')
    grid on
    axis([0  2    0  2    0  2])
    drawnow
    pause(0.25)
    xlabel('x [mm]')
    ylabel('y [mm]')
    zlabel('z [mm]')
end

.

[Fabio Taccaliti]

Thanks a lot, now it works :)

[Star Strider]

As always, my pleasure!

Answer 2

[Steven Lord]

Rather than recreating the scatter plot each time, I'd apply the first of the techniques listed on the Animation Techniques documentation page. If I ran this in MATLAB Answers you wouldn't see the animation, but if you run it in MATLAB you can.

% Sample data
theta = 0:15:360;
x = cosd(theta);
y = sind(theta);
% Create the initial "frame" of the animation
h = scatter(x, y, 'o');
% Control the axes so at its "widest" the whole circle still fits
axis([-5 5 -5 5])
% Make it look circular
axis equal
% At each frame, push each point outward (or pull it inwards)
for r = repmat([1:5 4:-1:2], 1, 10)
    % Update the existing object's properties rather than creating a new one
    h.XData = r*x;
    h.YData = r*y;
    % Let you see the animation
    pause(0.1)
end

In the "real" animation you might want to use one of the options for drawnow instead of pause.

[Fabio Taccaliti]

Thanks Steven, I'll have a better look into this :)