plot ( [-0.5, 1.5], [-0.5,1.5], 'g-', ...
       [-0.5, 1.5], [1.5,-0.5], 'b-', 'Linewidth', 3 );
grid on
xlabel ( '<---X--->', 'Fontsize', 16 )
ylabel ( '<---Y--->', 'Fontsize', 16 )
title ( '\xi_1([0,1];x) and \xi_2[0,1];x)','Fontsize', 24 )
axis ( [-0.5,1.5,-0.5,1.5] )
print ( '-dpng', 'xi1_and_xi2.png' );

