Getting Started

Creating Movies

If you increase the number of points in the Brownian motion example to something like n = 300 and s = .02, the motion is no longer very fluid; it takes too much time to draw each time step. It becomes more effective to save a predetermined number of frames as bitmaps and to play them back as a movie.

First, decide on the number of frames, say

• nframes = 50;
  

Next, set up the first plot as before, except using the default EraseMode (normal).

• x = rand(n,1)-0.5;
  y = rand(n,1)-0.5;
  h = plot(x,y,'.');
  set(h,'MarkerSize',18);
  axis([-1 1 -1 1])
  axis square
  grid off
  

Generate the movie and use getframe to capture each frame.

• 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
  

Finally, play the movie 30 times.

• movie(M,30)
  

Animations

Programming with MATLAB