How can I extract a single component from a Fourier decomposition of a 2D matrix and plot it as a 2D map?
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I have a scalar field (potential vorticity PV) on a 2-D square grid (599x599 cells).
I need to do a Fourier decomposition of the field and extract the contribution of the most important components.
Then, I have to plot the map of each component alone.
I would like to know how to extract the single components of the field and plot them as 2D (599x599) maps.
So far:
% Spatial sampling intervals
% (in km per pixel):
dx = 15;
dy = 15;
F1 = fft2(PV); % 2D Fourier Transform of the matrix PV
F2 = fftshift(F1); % zero-frequency component in the middle of the spectrum
imagesc(abs(F2)),colorbar
Not sure what to do after this.. any help would be appreciated!
2 commentaires
Rick Rosson
le 24 Mar 2015
Modifié(e) : Rick Rosson
le 24 Mar 2015
It would be helpful if you could provide the spatial sampling intervals in the x- and y directions (in units of distance per pixel, e.g. meters, cm, feet, or inches per pixel). For example:
% Spatial sampling intervals
% (in meters per pixel):
dx = 0.02;
dy = 0.03;
These parameters would allow you to calibrate the spatial frequency in the Fourier domain, which you will need to do to determine which spectral components are most prominent.
Réponses (1)
Rick Rosson
le 24 Mar 2015
Modifié(e) : Rick Rosson
le 24 Mar 2015
Here's a start:
[ M, N ] = size(PV);
Fs_x = 1/dx;
Fs_y = 1/dy;
dF_x = Fs_x/M;
dF_y = Fs_y/N;
Fx = -Fs_x/2:dF_x:Fs_x/2-dF_x + mod(M,2)*dF_x/2;
Fy = -Fs_y/2:dF_y:Fs_y/2-dF_y + mod(N,2)*dF_y/2;
F = meshgrid(Fx,Fy);
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