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Spectrum

Description

Computes the Fourier power spectrum of the input point set (Discrete Fourier Transform).

When the UTK_USE_FFTW cmake flag is set to true, the Fourier transform is computed using the fftw library (faster for high resolution spectra).

Note : functions and scripts returns a linear C-style array of the computed spectrum. Note : Only odd resolution are supported (so that the DC is properly identified). Note : When multiples pointset are given to ‘compute’, the results are averaged.

Files

src/metrics/Spectrum.cpp  
include/utk/metrics/PCF.hpp

Usage


Spectrum calculator
Usage: ./Spectrum [OPTIONS]

Options:
  -h,--help                   Print this help message and exit
  -i,--input TEXT:FILE ... REQUIRED
                              Input file(s)
  -o,--output TEXT            Output file (empty is stdout)
  -r,--res UINT [0]           Spectrum resolution (0 means automatic)
  --canceldc [0]              When set, cancel the DC peak
  --img TEXT                  When set, output image PNG of spectrum. Only available in 2D.
  --silent                    Silence UTK logs

#include <utk/utils/PointsetIO.hpp>
#include <utk/utils/Pointset.hpp>
#include <utk/samplers/SamplerWhitenoise.hpp>
#include <utk/metrics/RadialSpectrum.hpp>

int main()
{
    utk::Pointset<double> pts;

    utk::SamplerWhitenoise wn(2 /* dimension */);
    wn.setRandomSeed(/* empty means random, can also pass a number */);
    // Check for no errors

    auto spec = utk::Spectrum(
       101, // Resolution, only odd number. If even will use res - 1
       true // Cancel DC
    );
    if (wn.generateSamples(pts, 1024 /* Number of points */))
    {
        auto rslt = spec.compute(pts);
    }
}

import pyutk
import numpy as np

spec = pyutk.Spectrum(
  101, # Resolution, only odd number. If even will use res - 1
  True # Cancel DC
)
spec = spec.compute(np.random.uniform(0, 1, (128, 2)))

License

BSD, see Spectrum.hpp