Animate the terminator line through a year

Since version 8.
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See also Map, Date2JD, JD2DN, JDToDateString, TerminatorLine
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%--------------------------------------------------------------------------
%   Copyright (c) 2009 Princeton Satellite Systems, Inc.
%   All rights reserved.
%--------------------------------------------------------------------------

% make a movie?
makeMovie = 0; % set to 1 to create an avi movie of the animation
movieName = 'TerminatorLineMovie';

% apply shading?
shade = 1;

% create a 2D map of the Earth in a new figure
Map('Earth','2D')
hold on

% pick today as the starting date
jD   = Date2JD;
day0 = JD2DN(jD); % the starting day of the year (1 to 365)

% compute the terminator line for each day
n    = 100;
lat  = zeros(365,n);
sun  = zeros(2,365);
for i=1:365,
   [lat(i,:),long,sun(:,i)] = TerminatorLine( jD+i, n );
end

% day of the year vector
day = day0 + (1:365);
day(day>365) = day(day>365)-365;

ylim = 90;
if( day0>81 && day0<264 )
   ylim = -90;
end

% add terminator line, sun location and shaded patch to Earth map
t = line(long,lat(1,:),'color','y');
s = line(sun(2,1),sun(1,1),'color','y','marker','.','markersize',20);
if( shade )
   p = patch([-180 long 180],[ylim lat(1,:) ylim],'k');
   set(p,'facealpha',.5,'linestyle','none')
end

% animate
k = 0;
for i=1:2:365
   lat0 = sun(2,i);
   lon0 = sun(1,i);
   if( lon0<0 )
      eastWest = 'W';
   else
      eastWest = 'E';
   end
   if( lat0<0 )
      northSouth = 'S';
   else
      northSouth = 'N';
   end

   if( shade )
      % if latitude was initially outside 90 deg bound, must be winter
      if( day(i)>81 && day(i)<264 )
         ylim = -90;
      else
         ylim = 90;
      end
      set(p,'ydata',[ylim lat(i,:) ylim])
   end

   set(t,'ydata',lat(i,:))
   set(s,'xdata',sun(2,i),'ydata',sun(1,i))

   title(sprintf('Day/Night Across Earth at %s GMT \nSun at lon %s %2.1f / lat %s %2.1f  ',...
      JDToDateString(jD+i),eastWest,abs(lon0),northSouth,abs(lat0)))
   drawnow

   if( makeMovie )
      k=k+1;
      m(k) = getframe(gcf);
   end

end

% save movie to .avi file
if( makeMovie )
   SaveMovie(m,movieName)
end

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