Animate a scatter plot

What's the easiest way to create an animated scatter plot? I have a plot with over 20,000 points in my first scatter. These points shift their positions in a second scatter. I'd love to animate this shift. Is there a straightfoward way in Matlab to do this?

Answer 1

[VINAYAK LUHA]

Hi Gautam,

As per my understanding, you wish to animate the shift of scatter points between two scatter plots,

Here's a possible workaround,

xi = rand(1, 10);
xi = rand(1, 10);
yi = rand(1, 10);

xf = rand(1, 10);
yf = rand(1, 10);

figure;
ax = gca;
ax.NextPlot = 'replaceChildren';

axis([0 1 0 1]);
numFrames = 50;
for i = 1:numFrames
    % Calculate intermediate data
    t = i / numFrames; 
    xt = (1 - t) * xi + t * xf;
    yt = (1 - t) * yi + t * yf;
    
    % Plot scatter plot 
    scatter(xt, yt, [], [xt', yt', 1 - xt'], 'filled');
    hold on;
    for j = 1:numel(xt)
        plot([xi(j), xt(j)], [yi(j), yt(j)], 'Color', [xt(j), yt(j), 1 - xt(j)], 'LineWidth', 1.5);
    end
    hold off;
    
    frame = getframe(gcf);
    im = frame2im(frame);
    
    [imind, cm] = rgb2ind(im, 256);
    
    % Write the indexed image to GIF file
    if i == 1
        imwrite(imind, cm, 'animation.gif', 'gif', 'Loopcount', inf, 'DelayTime', 0.1);
    else
        imwrite(imind, cm, 'animation.gif', 'gif', 'WriteMode', 'append', 'DelayTime', 0.1);
    end

    if i==numFrames
        break
    end
    
    % Animation speed
    pause(0.01);
    cla
end

Hope this helps

[Gautam Sethi]

Thanks Vinayak, this is super helpful.

I have two questions about the code:

1. At the end of the code, it resets the figure to blank. I can't figure out why it does that and not end on the final coordinates.
2. Is there a way I could convert this animation to a gif and import it in PowerPoint?

Thanks again for your help.

[Walter Roberson]

xi = rand(1, 10);
yi = rand(1, 10);

xf = rand(1, 10);
yf = rand(1, 10);


figure;
ax = gca;
ax.NextPlot = 'replaceChildren';


axis([0 1 0 1]);


numFrames = 50;
for i = 1:numFrames
    % Calculate intermediate data
    t = i / numFrames; 
    xt = (1 - t) * xi + t * xf;
    yt = (1 - t) * yi + t * yf;
    
    % Plot scatter plot 
    scatter(xt, yt, [], [xt', yt', 1 - xt'], 'filled');
    hold on;
    for j = 1:numel(xt)
        plot([xi(j), xt(j)], [yi(j), yt(j)], 'Color', [xt(j), yt(j), 1 - xt(j)], 'LineWidth', 1.5);
    end
    hold off;
    
    if i ~= numFrames        %do not clear at the end
        % Animation speed
        pause(0.1);
       
        cla;
    end
end

[VINAYAK LUHA]

Hi Gautam,

Regarding your questions -

1. The "cla" commands at the end in the loop clears the current axis from all the graphics object, including the lines and points,hence the blank figure.If you want the animation to stop at the final points, just put a condition on "cla" command for the final frame.
2. Yes you can convert the axis/figure to indexed images and save it as a ".gif" file.

I've updated the code as per the discussion.

[Gautam Sethi]

Wow, Vinayak, that's amazing! I can't thank you enough for writing ths code.

[Gautam Sethi]

Thank you, Walter. I appreciate your assistance. I have a better understanding of writing animations now.