i dont know why the second figure is empty

fs=20;
Ts=1/fs;
N=1024
Tmax=(N-1)*Ts;
t=-10:Ts:10;
ut=exp(-(t/10).^2);
plot(t,ut.^2)
f=-5:fs:5;
z=fftshift(fft(ut));
plot(f,abs(z))

Answer 1

[Azzi Abdelmalek]

Figure 1 was erased by figure 2

fs=20;
Ts=1/fs;
N=1024
Tmax=(N-1)*Ts;
t=-10:Ts:10;
ut=exp(-(t/10).^2);
%-----figure 1--------------
plot(t,ut.^2)
% -----figure 2------------
figure
z=fftshift(fft(ut));
plot(abs(z))

Check this

 f=-5:fs:5

[abed]

very nice i need to ask 2 things: the axis of the second figure how did it work out for you without introducing fs? second if i want to show the propagation of this signal in 3d length frequency and intensity what should i do any thoughts??