function ShowRect(R,s)
% R is rectangle
% s is one of the characters 'k','w','r','g','b','m','c','y'
% Displays R in the current figure window using the color s
% Assumes hold is on

fill([R.left R.right R.right R.left],[R.bot R.bot R.top R.top],s)
plot([R.left R.right R.right R.left R.left],...
     [R.bot R.bot R.top R.top R.bot], 'k','Linewidth',2)