function h = drawbox(center,a,b,color);
%
%  Draw a box and return its handle
%  Inputs
%     center = x,y locations of center
%     a,b = side lengths
%     color = optional color
%
%  Output
%     h = graphic handle which can be used to move the box
%
error(nargchk(3,4,nargin));
if nargin < 4
    color = 'b';
end;
x = center(1) + (a/2)*[-1 1 1 -1 -1];   % Counter-clockwise from lower left
y = center(2) + (b/2)*[-1 -1 1 1 -1];
h = plot(x,y,'Color',color);