function AnimateBridge(y)
%Animates the Tacoma Narrows Bridge from the solution to the differential
%equation, y.  Time is assumed to be varying by a fixed step h...
%
%  Length (len) is fixed at 6 below and in the ODEs
%

clf % clear figure window

len=6;
set(gca,'XLim',[-8 8],'YLim',[-8 8], 'XTick',[-8 0 8],'YTick',[-8 0 8], ...
'Drawmode','fast','Visible','on','NextPlot','add');

cla; % clear screen
axis square % make aspect ratio 1 - 1
road=line('color','b','LineStyle','-','LineWidth',5,'erase','xor','xdata',[],'ydata',[]);
lcable=line('color','r','LineStyle','-','LineWidth',1,'erase','xor','xdata',[],'ydata',[]);
rcable=line('color','r','LineStyle','-','LineWidth',1,'erase','xor','xdata',[],'ydata',[]);

[mm,nn]=size(y);  %y should be tall, nn should be 4
if mm<nn
    y=y';
    [mm,nn]=size(y);
end
if nn~=4
    error('Number of Variables should be 4');
end

for k=1:mm
   c=len*cos(y(k,3)); s=len*sin(y(k,3));
   set(road,'xdata',[-c c],'ydata',[-s-y(k,1) s-y(k,1)])
   set(lcable,'xdata',[-c -c],'ydata',[-s-y(k,1) 8])
   set(rcable,'xdata',[c c],'ydata',[s-y(k,1) 8])
   drawnow; pause(0.04)
end