xlist = linspace ( -0.5, 1.5, 101 );
ylist = 4 * xlist - 3;
plot ( xlist, 0*ylist, 'k:', ...
       [0.0, 0.0], [ 0.0, -3.0], 'b-', ...
       [1.0, 1.0], [ 0.0,  1.0], 'b-', ...
       0.0, -3.0, 'b.', ...
       1.0,  1.0, 'b.', ...
       'Linewidth', 3, 'Markersize', 50 );
grid on
xlabel ( '<-- X -->' )
ylabel ( '<-- Y -->' );
title ( 'Two data points available', 'Fontsize', 24 );
axis ( [-0.5,1.5,-5,3] );
print ( '-djpeg', 'secant_ill1.jpg' );

