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Radially averaged power spectrum of 2D real-valued matrix

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12 Apr 2009 (Updated )

Computes and plots radially averaged PSD of 2-D real matrix with a given spatial resolution.

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Description

The radially averaged power spectrum (RAPS) is the direction-independent mean spectrum, i.e. the average of all possible directional power spectra. The radially averaged power spectrum provides a convenient means to view and compare information contained in 2-D spectra in 1-D. This function computes and plots the RAPS of an input matrix (does not consider corner values outside averaging radius). The image can be rectangular but must be 2-D (e.g., multi-color channel data is not supported). The spatial resolution of the data is also specified.

MATLAB release MATLAB 7.3 (R2006b)
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Comments and Ratings (6)
19 Apr 2014 Jim Kasson  
17 Apr 2013 Joao Marcos

Also, even my region is ~1000km the spectrum shows energy up to 5000km...

17 Apr 2013 Joao Marcos

Thank you for the file, it was very usefull.
I runned a test where I linearly interpolate a 50km wind data to 5km. I would expect a drop in the energy at 100km, but the spectra shows eenrgy cascating down to the 5km scale. Do you know why this happens?
Thank you

03 Apr 2013 fong

useful for understanding RAPSD to analysis the spectral characteristics of a halftone pattern?

16 Aug 2011 Angjelina Protik

for r = 0:floor(dimMax/2)
i{r + 1} = find(rho == r);
end
Pf = zeros(1, floor(dimMax/2)+1);
for r = 0:floor(dimMax/2)
Pf(1, r + 1) = nanmean( imgfp( i{r+1} ) );
end
there is some bug in this part

06 Apr 2011 Stefano

Hi, I found this to be faster, hope it helps, S.
%% code for fast radial averaging:
[xx,yy]=meshgrid(-1000:1000,-1000:1000);
rr=sqrt(xx.^2+yy.^2);
ri=floor(rr/100)+1;
N=numel(ri);
[~,~,iir]=unique(ri); %find unique values
Qt =sparse(1:N,iir,ones(N,1));

tic;Pf=(rr(:).'*Qt).';toc %radial average

Updates
15 Apr 2009

The radially averaged power spectrum provides a convenient means to view and compare information contained in 2D spectra in 1D.

17 Jun 2009

Rectangular matrices can now be input; spatial resolution can be specified.

17 Jun 2009

Fixed bug in x-axis of plot; preallocated memory for axes label cells; removed minor ticks from y-axis; cleaned up comments.

16 Mar 2011

Added feature to handle odd/even dimensionality differences of input matrix

17 Mar 2011

Clarified restrictions on input to the file description (e.g., multi-channel data from JPG, etc. is not supported)

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