%%%%%%%%%%%%%%%%%%%%%    Unit Circle Plot  %%%%%%%%%%%%%%%%%%%%%
%
% BOUNDARY
% Usage: BOUNDARY(toptitle,bottitle,col);
%
% Inputs:  totptitle, bottitle - titles for the top and bottom
%          col - color of the boundary
%
%          The unit circle with appropriate titles and color is plotted
%          The graphics screen is also initialized for further plots
 
   function h = boundary(toptitle,bottitle,col)
   clf 
   t=0:(2*pi)/300:2*pi;                % angles
   x = cos(t);  y = sin(t);            % cosines and sines
   plot(x,y, [':',col]);
   axis equal
   axis off
   title(toptitle);     
   xlabel(bottitle);
   hold on
   set(gcf,'DefaultLineEraseMode','none');
   set(gcf,'NextPlot','add');
   dum = [];                           % dummy return value   
   clear t;
   clear x;
   clear y;