How to speed up the plot?

How to speed up the plot?

http://www.mathworks.co.uk/moler/exm/exm/bouncer.m

Here is the code if you are too lazy to download it :P :

function bouncer
% BOUNCER  Simple illustration of gravity.

     [z0,h] = initialize_bouncer;
     g = 9.8;        % Gravity
     c = 0.75;       % Elasticity
     delta = 0.005;  % Time step
     v0 = 21;        % Initial velocity
     while v0 >= 1
        v = v0;
        z = z0;
        while all(z >= 0)
           set(h,'zdata',z)
           drawnow
           v = v - delta*g;
           z = z + delta*v;
        end
        v0 = c*v0;
     end
     finalize_bouncer

end

%-----------------------------------------------

function [z,h] = initialize_bouncer
% INITIALIZE_BOUNCER
%  The z-coordinates and the handle for a surf plot of a sphere.
   clf
   shg
   set(gcf,'color','white','numbertitle','off','name','  Bounce')
   axes('position',[0 0 1 1])
   [x,y,z] = sphere(20);
   z = z + 1;
   h = surf(x,y,z);
   colormap copper
   shading interp
   axis([-12.5 12.5 -12.5 12.5 0 25.0])
   axis square off
   view(90,0)
   uicontrol('string','TOSS','style','pushbutton', ...
      'units','normal','position',[.10 .05 .12 .05], ...
      'background','white','fontweight','normal', ...
      'enable','off','callback','bouncer')
   drawnow
end

%-----------------------------------------------

function finalize_bouncer
   set(findobj('string','TOSS'),'fontweight','bold','enable','on')
end

Answer 1

[Daniel Shub]

IT smells like homework to me ... I hope I am wrong. Can you see how this might help.

cnt = cnt+1;
if ~rem(cnt, 4)
  set(h,'zdata',z)
  drawnow
end

[BabyMilo]

This is not homework :)

Im just learning matlab by myself at the moment.

I can make the plot quicker using your code but can you explain what does to?

Many thanks.

[BabyMilo]

what does it do*

i mean

[Daniel Shub]

The slow part of the code is the plotting (specifically the drawnow which causes the screen to refresh). You can see how fast it runs if you comment out the set and drawnow commands. The code I gave causes the screen to only be updated every 4 frames. If you change the 4 to a bigger number you can make the code go faster, but the "movie" will be jumpy.