Hold on does not work

Hi everyone,

I have a probleme with plotting a graph. Indeed, I do not understand why my function "Hold on" does not work.

Here is my script.

Nmin = 2;
Nmax = 100;
abscisses = (Nmin:Nmax);
for N=Nmin:Nmax
    A=matrice_A(N);
    ordonnees(N-Nmin+1)=cond(A);
end

plot(abscisses,ordonnees,'b'); 
hold on;
plot(abscisses,(4/(pi^2))*(abscisses+1).^2,'r');

Here is my function matrice_A .

function [ A ] = matrice_A( N )

A = diag(2*ones(1,N),0)-diag(ones(1,N-1),-1)-diag(ones(1,N-1),1);

end

Thanks for advance !!

[Jan]

Please explain, what "does not work" means. What do you observe? What is the problem?

Answer 1

[Walter Roberson]

Look at

Nmin = 2;
Nmax = 100;
abscisses = (Nmin:Nmax);
for N=Nmin:Nmax
    A=matrice_A(N);
    ordonnees(N-Nmin+1)=cond(A);
end

plot(abscisses,ordonnees,'b'); 
hold on;
o2 = (4/(pi^2))*(abscisses+1).^2;
plot(abscisses,o2,'r');  
figure();
plot(abscisses, ordonnees - o2, 'g');

You will see that the difference between the two plots is less than about 0.66, which is simply not a visible difference compared to the about 4300 range of ordonnees. If you zoom way in on the first plot you can see that the two lines are both there.