function DrawStar(xc,yc,c)
% Adds a regular octagon to the current figure window.
% Assumes hold is on.
% The octagon has radius 1, center(xc,yc) and
% color c where c is one of 'r', 'g', 'y', etc.
% Set up the vertices...
tau = pi/4;
for k=1:9
theta = (k-1/2)*tau
x(k) = xc + cos(theta);
y(k) = yc + sin(theta);
end
fill(x,y,c)