nframes = 50;
x = rand(n,1)-0.5;
y = rand(n,1)-0.5;
h = plot(x,y,'.');
set(h,'MarkerSize',100);
axis([-1 1 -1 1])
axis square
grid on
for k = 1:nframes
x = x + s*randn(n,1);
y = y + s*randn(n,1);
set(h,'XData',x,'YData',y)
M(k) = getframe;
end
movie(M,30)