function ident_example0(L,std_e)

n = 2;
N = L - n;

theta = [-0.34 0.6 0.3369 0.4800]';

t = [1:1:L]';

u = idinput(L,'PRBS',[0 1],[-1 1]);

% std(u) % deviazione standard ingresso

Bz = [0  theta(4)  theta(3)];
Az = [1 -theta(2) -theta(1)];

ys = dlsim(Bz,Az,u);

randn('state',0)
e = std_e * randn(L,1);

% std(e) % deviazione standard errore d'equazione

ef = dlsim([0 0 1],Az,e); % filtraggio dell'errore d'equazione

y = ys + ef;

figure, subplot(211), plot(t,u,'-'), xlabel('Campioni'), title('Ingresso u')
        subplot(212), plot(t,y,'-'), xlabel('Campioni'), title('Uscita y')
        

        
% roots(Az) % verifica la stabilita' del polinomio       


Phi_u = my_hank(u,N,n,0);        
Phi_y = my_hank(y,N,n,0);
Phi   = [Phi_y Phi_u];
Y     = y(n+1:N+n);

theta

disp(sprintf('\n'))

theta_hat = inv(Phi' * Phi) * Phi' * Y 

disp(sprintf('\n'))

Yhat = Phi * theta_hat;

eps_err = Y - Yhat;

sigma_e_hat = (1/(N - length(theta)))*(eps_err' * eps_err);

% std_e_hat = sqrt(sigma_e_hat) % stima dell'errore d'equazione

cov_theta_hat = sigma_e_hat * inv(Phi' * Phi);

disp(sprintf('\n'))

std_err_theta = sqrt(diag(cov_theta_hat))


figure, subplot(221), plot(theta(1),'b*'), hold on, plot(theta_hat(1),'ro'), 
                      hold on, plot(theta_hat(1) + std_err_theta(1),'g^'), 
                      hold on, plot(theta_hat(1) - std_err_theta(1),'gv'), 
                      title('a_2')
        
        subplot(222), plot(theta(2),'b*'), hold on, plot(theta_hat(2),'ro'), 
                      hold on, plot(theta_hat(2) + std_err_theta(2),'g^'), 
                      hold on, plot(theta_hat(2) - std_err_theta(2),'gv'), 
                      title('a_1')              

        subplot(223), plot(theta(3),'b*'), hold on, plot(theta_hat(3),'ro'), 
                      hold on, plot(theta_hat(3) + std_err_theta(3),'g^'), 
                      hold on, plot(theta_hat(3) - std_err_theta(3),'gv'), 
                      title('b_2')    
                      
        subplot(224), plot(theta(4),'b*'), hold on, plot(theta_hat(4),'ro'), 
                      hold on, plot(theta_hat(4) + std_err_theta(4),'g^'), 
                      hold on, plot(theta_hat(4) - std_err_theta(4),'gv'), 
                      title('b_1')                        


return

%%%%%%%%%%%%%%%%%%%%%%% Funzioni Locali %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

function Hn = my_hank(Yvet,Nseq,Ord,Off)

  for i=1:Ord,

      Hn(:,i) = Yvet( Off+i: Nseq+Off+i-1 );

  end;
  
return