x0 = 0 ;
y0 = 1 ;
X  = 2 ;
N  = 30 ;
[x,ye] = Eulero_esplicito (@test_1_yp,x0,y0,X,N) ;
[x,yc] = Collatz          (@test_1_yp,x0,y0,X,N) ;
[x,yh] = Heun             (@test_1_yp,x0,y0,X,N) ;
hold off ;
plot(x,ye,'.-b');
hold on ;
plot(x,yc,'.-k');
plot(x,yh,'-gs');
x = [x0:(X-x0)/200:X];
plot(x,test_1_esatta(x),'-r','LineWidth',2);
legend('Eulero',  ...
       'Collatz', ...
       'Heun',    ...
       'Esatta');
