clear all
close all

mode = 0; % figure version
%mode = 1; % demo  version

if (mode)
   phi = input('Phi in degrees: ');
else
   phi = 20;
end

for phi = 0:5:360
   phi
   phi = pi*phi/180;

   l = 2; % length of axes

   x = 1;
   y = 1;

   xp = x*cos(phi) + y*sin(phi);
   yp = x*sin(phi) - y*cos(phi);

   hold on

   figure(1)
   plot([-l,l],[0,0],'k-') % lab x-axis
   plot([0,0],[-l,l],'k-') % lab y-axis
   plot([0,x,0,x] ,[0, 0, y, y],'ko') % points in the rotated system
   plot([0,1,1],[1,1,0],'k--') % lab impulses
   plot([-l*sin(phi),l*sin(phi)],[l*cos(phi),-l*cos(phi)],'b-') % rotated axes
   plot([-l*cos(phi),l*cos(phi)],[-l*sin(phi),l*sin(phi)],'b-') % rotated axes
   plot(yp*sin(phi),-yp*cos(phi),'b*') % points in the rotated system
   plot(xp*cos(phi),xp*sin(phi),'b*') % points in the rotated system
   plot([yp*sin(phi),1,xp*cos(phi)],[-yp*cos(phi),1,xp*sin(phi)],'b--') % lab impulses
   axis off
   axis equal
   hold off
   if (phi < pi*20/180)
      pause
   else
      pause(0.5)
   end
   close(1)
end