How to create and plot a Gaussing function?

Hello ,

i want to create a 2D Gaussian function 9x9 and sigma =0.7 using this type :

Here is my code:

sigma=0.7;
nx=9;
ny=9;
[x,y]=meshgrid(1:nx,1:ny);

G=(0.5/(pi.*(sigma.^2))).*exp(-0.5.*((y.^2+x.^2)./(sigma.^2)));

Then i was asked to take the Gaussian function G and compute its fast fourier transform by using fft2()

G_fft=fft2(G);

Finally by using mesh() i was asked to compare the 2 results .

figure();
mesh(G);
figure();
mesh(G_fft);

The problem here is that in the first case (mesh(G)) i am getting a big edge(which i dont know if its right) and in the second case i am getting this error : X, Y, Z, and C cannot be complex. (problem in the line mesh(G_fft) because G_fft has complex numbers due to fourier transform).

Can comeone tell me what is wrong here?

[Gn Gnk]

This is what i get using mesh() for ploting the Gaussian function

Answer 1

[VBBV]

%true
sigma=0.7;
nx=9;
ny=9;
[x,y]=meshgrid(-nx:0.5:nx,-ny:0.5:ny);
G=(0.5./(pi.*(sigma.^2))).*exp(-0.5.*((y.^2+x.^2)./(sigma.^2)));  
G_fft=fft2(G);
figure(1);
mesh(x,y,G);
figure(2);
mesh(x,y,abs(G_fft));

Use both positive and negative values for meshgrid to get Gaussian shape as above. Use also _abs_instead of real value e

[Gn Gnk]

Perfect thank you so much !!

Just a quick notice :

nx and ny should be equal to 2 in order for G to be 9x9 .

Can you explain why the plots appear to be opposite (i think)