# Help in implementing of peak function in Fourier transform

I have a function Peak function

I know how to implement it in time range just need to caclulate $r$. first I initial $x$, y with a range and meshgrid them, after it calculate $r$

x=-2:1/100:2;
y=-2:1/100:2;
[x,y]=meshgrid(x,y);
r=sqrt(x.^2 + y.^2);
Peak=1./r;


but when I want go to frequency domain, what is $f$ and how it should be initial?

appreciate any urgent help :(

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