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/* Polynomial_to_Spectrum.h
*
* Copyright (C) 2020 David Weenink
*
* This code is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This code is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
*/
#include "Polynomial_to_Spectrum.h"
static void Polynomial_evaluate_z_cart (Polynomial me, double r, double phi, double *out_re, double *out_im) {
longdouble rn = 1.0;
longdouble re = my coefficients [1];
longdouble im = 0.0;
if (r == 0.0)
return;
for (integer i = 2; i <= my numberOfCoefficients; i ++) {
rn *= r;
const longdouble arg = (i - 1) * phi;
re += my coefficients [i] * rn * cos (arg);
im += my coefficients [i] * rn * sin (arg);
}
if (out_re)
*out_re = (double) re;
if (out_im)
*out_im = (double) im;
}
/* Can be speeded up by doing a FFT */
autoSpectrum Polynomial_to_Spectrum (Polynomial me, double nyquistFrequency, integer numberOfFrequencies, double radius) {
try {
Melder_require (numberOfFrequencies > 1,
U"Number of frequencies should be greater than 1.");
autoSpectrum thee = Spectrum_create (nyquistFrequency, numberOfFrequencies);
const double phi = NUMpi / (numberOfFrequencies - 1);
for (integer i = 1; i <= numberOfFrequencies; i ++) {
double re, im;
Polynomial_evaluate_z_cart (me, radius, (i - 1) * phi, & re, & im);
thy z [1] [i] = re;
thy z [2] [i] = im;
}
return thee;
} catch (MelderError) {
Melder_throw (me, U": no Spectrum calculated.");
}
}
/* End of file Polynomial_to_Spectrum.cpp */
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