[Moreza7]

I have 192 grids of two point correlation data of a 3.14(m) length domain.
I use the "fft" command in matlab to plot the energy spectrum. How can I calculate wavenumber(k) of each grid?

R= load('2pcor.txt');
 PHI = fft(R); 

% K=?? ; 

%loglog(K,abs(PHI));

[FMDenaro]

Originally Posted by KevinSpears

I have 192 grids of two point correlation data of a 3.14(m) length domain.
I use the "fft" command in matlab to plot the energy spectrum. How can I calculate wavenumber(k) of each grid?

R= load('2pcor.txt');
 PHI = fft(R); 

% K=?? ; 

%loglog(K,abs(PHI));

On your grid of Nx=192 nodes you have 192/2=96 resolvable wavenumbers. Each wavelength is k=n*2*pi/L. Thus, if you L is exactly pi (in meters) you have k=2*n. The maximum in your range is the Nyquist frequency pi/h=pi/(L/Nx)=Nx