Animations of several points

I am trying to simulate the trajectories of a few particles in 2D on Matlab. I have the x- and y- coordinates of these particles as a function of time, which I store as matrix x and y. The column in both x and y corresponds to the time, while the row corresponds to the particle number: 1, 2, etc.

I know how to do the animation for one particle, but I am not sure how to customize the code for multiple particles' trajectories. Basically, my idea is that on the initial plot, I have 3 markers which correspond to the initial position of the particles, say particle A, B and C. Then, I would like to follow the movement of these 3 markers, and here is where I encountered the problem: I don't know how to sort the subsequent points according to the particle identity. For example, I want to specify the first point I plot in the second time point as particle A, second point as particle B and third point in particle C.

I have tried this but this will simulate the trajectory particle by particle, and then erase the data when the next particle is simulated. I would like to plot all of these trajectories on the same plot.

% for i = 1:nPart
%     for ii = 1:length(x(i,:))
%         pause(0.01)
%         set(h, 'XData', x(i,1:ii), 'YData', y(i,1:ii));
%         drawnow %// you can probably remove this line, as pause already calls drawnow
%         hold all
%     end
% end

Any idea will be greatly appreciated. Thank you!

[Image Analyst]

Do you just want to display the curves? Or do you want the individual data points to draw slowly, like it's an animation?

[Cheetezz]

Individual data points to show up slowly, creating an animation of trajectories from starting point to the end point

Answer 1

[Image Analyst]

Try something like this:

y = rand(3, 20); % Generate random sample data.
x = rand(size(y, 1), size(y, 2));
% Now we have x and y sample data and we can begin.
% Extract into separate arrays
x1 = sort(x(1,:));
x2 = sort(x(2,:));
x3 = sort(x(3,:));
y1 = y(1,:);
y2 = y(2,:);
y3 = y(3,:);
for k = 1 : length(x1)
  plot(x1(1:k), y1(1:k), 'r*-', 'LineWidth', 2);
  xlim([min(x(:)), max(x(:))]);
  ylim([min(y(:)), max(y(:))]);
  grid on;
  hold on;
  plot(x2(1:k), y2(1:k), 'g*-', 'LineWidth', 2);
  plot(x3(1:k), y3(1:k), 'b*-', 'LineWidth', 2);
  hold off;
  fprintf('Plotted points 1 through %d\n', k);
  pause(0.8);  
end  
fprintf('Done!\n');

[Cheetezz]

This works alright for 3 particles. However, in my system I may change the number of particles to 100 for example and therefore I won't be able to create the xi and yi vectors 100 times. Is there a way that I can automate this? Thanks!

[Image Analyst]

Sure, just add an outer for loop over the rows of x and extract each x and y from the larger array before you plot it.

[Cheetezz]

I am still unclear about that. Won't that erase particle A's trajectory before the particle B's trajectory is drawn? I would like to plot all the particles simultaneously at a certain time point, and I thought that the use of for loop across the number of particles will just plot the animation sequentially rather than simultaneously. I may be thinking about this wrongly, but it would be great if you can provide me an example of what you thought would work!

[Utkarsh Anand]

You can use a structured approach to create 'n' empty cells; something like::

Particles = struct();

Cheers