hold off ;
beta = -0.5 ;
x = [-2:0.01:2] ;
plot(x,q0(x),'.-b','LineWidth',1.5) ; hold on ;
plot(x,esatta(x,1,beta,@q0),'+-r') ; hold on ;
plot(x,esatta(x,2,beta,@q0),'o-y') ; hold on ;
plot(x,esatta(x,3,beta,@q0),'.-m') ; hold on ;
plot(x,esatta(x,4,beta,@q0),'.-g') ; hold on ;

legend('p0','t=1','t=2','t=3','t=4');
axis([-2,2,-0.1,1.1]);