function [] = prob_13_11_d()
% 
% Written by:
% -- 
% John L. Weatherwax                2006-09-06
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

close all; 

% the state "v" is defined as v = (q,u):
%
v_l = [ 0.5 -1 ]; 
v_r = [ 1    1 ]; 

q = linspace( 0.01, 2, 100 ); 

figure; hold on; 

% plot the state v_l:
%
hsvl = plot( v_l(1), v_l(2), 'b.', 'MarkerSize', 15 ); 

% plot one-integral/Hugoniot curves through v_l:
%
qu_prod = v_l(1)*v_l(2);
u1 = qu_prod ./ q;
hvlc = plot( q, u1, '-b' ); 

% plot the state v_r:
%
hsvr = plot( v_r(1), v_r(2), 'r.', 'MarkerSize', 15 );

% plot two-integal/Hugoniot curves through v_r:
%
u2 = repmat(v_r(2),1,length(q)); 
hvrc = plot( q, u2, '-r' ); 

% Add some labels:
%
axis( [ 0 2 -15 5 ] ); 
xlabel( 'q' ); ylabel( 'u' ); grid on; 
legend( [ hsvl hvlc hsvr hvrc ], { ...
    '(q_l,v_l)', 'wave curve through v_l', ...
    '(q_r,v_r)', 'wave curve through v_r' }, 'Location', 'SouthEast' );
saveas( gcf, 'prob_13_11_pt_d.eps', 'psc2' );