% Simulation for Brown motion
n=20;
s=.02;
x=rand(n,1)-0.5;
y=rand(n,1)-0.5;
h=plot(x,y,'.');
    axis([-1 1 -1 1])
    axis square
    grid off
    set(h, 'EraseMode', 'xor', 'MarkerSize', 18)

while 1
drawnow
x=x+s*(rand(n,1)-0.5);
y=y+s*(rand(n,1)-0.5);
set(h,'XData',x,'YData',y)
end

clc