How to keep axes box fixed when creating an animation

Hi,

I have data from ode45 that I want to plot in space at every time step. To do this, I create a for loop over the time output from ode45 and plot the position at every point. Here is my code:

for i=1:length(t)
  plot3(x(:,1,i),x(:,2,i),x(:,3,i),'k*')
  hold on
  plot3(x(:,1,i)+d(:,1,1,i),x(:,2,i)+d(:,2,1,i),x(:,3,i)+d(:,3,1,i),'k*')
  grid on
  axis equal
  xlabel('x')
  ylabel('y')
  zlabel('z')
  camtarget([0 0 0])
  campos([2 2 L/2])
  camup([1 0 0])
  axis([-1.2,1.2,-1.2,1.2])
  hold off
  drawnow
end

This works pretty well, but, despite my definition for the axis limits, the plot box deforms as I iterate through time. How can I keep it rigid?

Answer 1

[Ameer Hamza]

Every time you call plot3(), you are actually creating a new axes object. The new axis object will overwrite the properties of previous axes hence axis([-1.2,1.2,-1.2,1.2]) while no longer be effective. The proper way is to use line handle to update the animation. Use following code as template

l1 = plot3(0,0,0);
l1.XData = [];
l1.YData = [];
l1.ZData = [];
l1.LineStyle = 'none';
l1.MarkerEdgeColor = 'r';
l1.Marker = '*';

hold on

l2 = plot3(0,0,0);
l2.XData = [];
l2.YData = [];
l2.ZData = [];
l2.LineStyle = 'none';
l2.MarkerEdgeColor = 'g';
l2.Marker = '*';

axis([0 1 0 1 0 1]);

for i=1:100
  l1.XData = rand(1, 100);
  l1.YData = rand(1, 100);
  l1.ZData = rand(1, 100);
  l2.XData = rand(1, 100);
  l2.YData = rand(1, 100);
  l2.ZData = rand(1, 100);
  pause(1);
end

[Roy Goodman]

This makes sense to me for plotting a single line object, or even if a fixed number of line objects.

I am writing a function that creates an animation from a numerical data set which may have an arbitrary number of line objects at each step. In my case the number of lines is fixed from frame to frame within an animation, but will vary between two animations.

[Roy Goodman]

Nevermind. The obvious answer, cell arrays, works great. Just replace l1 and l2 in the above code with l{1} and l{2}.