why i am getting a blank graph

omega_bar = (0:0.01:5)';
n_omega_bar = size(omega_bar,1); 
for i = 1:n_omega_bar
    OMG = omega_bar(i,1);
    Y_bar = (OMG.^2)/(1-OMG.^2)
    
end
figure(1)
plot(omega_bar,abs(Y_bar(1,:)),'o')
xlim([0 5])
ylim([0 8*1e14]);

Answer 1

[Walter Roberson]

    Y_bar = (OMG.^2)/(1-OMG.^2)

That overwrites all of Y_bar each time. You need

    Y_bar(1,i) = (OMG.^2)/(1-OMG.^2)

But your code could be simplified:

    Y_bar = omega_bar.^2 ./ (1-omega_bar.^2);
    

No loop is needed.