MATLAB: Plotting random vectors

plotting vectors random generation

Just a heads up, I have virtually no matlab experience. I need to generate a an XY-plane where a random number 'n' vectors will be plotted. How do I do this?

Also, after they are plotted I want to iterate the function so that every time I hit enter the graph will update moving the vectors in a certain manner based on the following two functions: (x_i is the i^th particle's position) x_i(t + 1) = x_i(t) + v_i(t)(t-t_0) as position

(i^th particles direction) theta(t+1) = theta(t)_r

where theta(t)_r denotes the average direction of velocities of of the particles surrounding the ith particle being within a circle of radius r.

Hopefully this would eventually make all the vectors point in the same direction and cluster to a certain area.

Thanks in advance

Best Answer

R = rand(N) returns an N-by-N matrix containing pseudorandom values drawn from the standard uniform distribution on the open interval(0,1).

You could draw your vectors from R by random coordinates for every vector. For plotting consider using the file:

http://www.mathworks.com/matlabcentral/fileexchange/7470

If you need to update the plot, put a 'hold on' command after plotting the initially generated vectors. Then update the coordinates based on the requirement you mention. In a loop I would see this simple solution working.

I hope it helps!

Best regards, Poul Reitzel

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Yes. I would do something like this:

figure(1)
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MATLAB: 2D random walk double for loop

I used the following method to generate the x and y coordinates od 2000 points moving randomly in 2D cartesian space. I was then able to use the "plot" function to track their movement.

pos_x = zeros(1, 2000);
pos_y = zeros(1, 2000);
d = 0.01;
 
for i = 1:2000
theta = 2*pi*rand(1, 2000);
pos_x(end + 1, :) = pos_x(end) + d.*cos(theta);
pos_y(end + 1, :) = pos_y(end) + d.*sin(theta);
end
 
% pos_x(i, j) = X-cooridnate of the jth particle at instance 'i'.
% pos_y(i, j) = Y-cooridnate of the jth particle at instance 'i'.

The next thing would be to plot the particle's movements in the cartesian plane.

for i = 1:2000
plot(pos_x(:, i), pos_y(:, i));
hold on;
end

Plotting all the 2000 points on the same figure can get messy though. I suggest plotting 3-5 of them at a time.

Here is some additional material I found related to visualizing random walks:

https://www.mathworks.com/videos/visualizing-random-walk-data-part-1-97175.html

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