How can I draw a Frequency-Domain?

Hi,

I encounter the problem of transforming a shape from the time domain to the frequency domain.

I used the following commands to convert Fourier.

n1=8;

n2=72;

nt=25501;

dt=1.176470588235294e-13;

F=zeros(n1+n2+2,nt);

F1=F(n1+n2,:);

F2 = fftshift(fft(F1));

f=linspace(-10,10,length(F2));

figure(1);

plot(f, 10*log10(abs(F2)))

Please do not doubt the values entered such as 'nt' and 'dt' because all the shapes obtained in the time domain are correct and the only problem is in converting the frequency.

Let me know please.

Thank you.