fftn.cc

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////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2004-2025 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave 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 3 of the License, or
// (at your option) any later version.
//
// Octave 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
// <https://www.gnu.org/licenses/>.
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////////////////////////////////////////////////////////////////////////
 
#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif
 
#include "lo-mappers.h"
 
#include "defun.h"
#include "error.h"
#include "errwarn.h"
#include "ovl.h"
#include "utils.h"
 
OCTAVE_BEGIN_NAMESPACE(octave)
 
// This function should be merged with Fifft.
 
static octave_value
do_fftn (const octave_value_list& args, const char *fcn, int type)
{
  int nargin = args.length ();
 
  if (nargin < 1 || nargin > 2)
    print_usage ();
 
  octave_value retval;
  octave_value arg = args(0);
  dim_vector dims = arg.dims ();
 
  for (int i = 0; i < dims.ndims (); i++)
    if (dims(i) < 0)
      return retval;
 
  if (nargin > 1)
    {
      Matrix val = args(1).xmatrix_value ("%s: SIZE must be a vector of length dim", fcn);
 
      if (val.rows () > val.columns ())
        val = val.transpose ();
 
      if (val.columns () != dims.ndims () || val.rows () != 1)
        error ("%s: SIZE must be a vector of length dim", fcn);
 
      for (int i = 0; i < dims.ndims (); i++)
        {
          if (math::isnan (val(i, 0)))
            error ("%s: SIZE has invalid NaN entries", fcn);
          else if (math::nint_big (val(i, 0)) < 0)
            error ("%s: all dimensions in SIZE must be greater than zero", fcn);
          else
            dims(i) = math::nint_big(val(i, 0));
        }
    }
 
  if (dims.any_zero ())
    {
      if (arg.is_single_type ())
        return octave_value (FloatNDArray (dims));
      else
        return octave_value (NDArray (dims));
    }
 
  if (arg.is_single_type ())
    {
      if (arg.isreal ())
        {
          FloatNDArray nda = arg.float_array_value ();
 
          nda.resize (dims, 0.0);
          retval = (type != 0 ? nda.ifourierNd () : nda.fourierNd ());
        }
      else
        {
          FloatComplexNDArray cnda = arg.float_complex_array_value ();
 
          cnda.resize (dims, 0.0);
          retval = (type != 0 ? cnda.ifourierNd () : cnda.fourierNd ());
        }
    }
  else
    {
      if (arg.isreal ())
        {
          NDArray nda = arg.array_value ();
 
          nda.resize (dims, 0.0);
          retval = (type != 0 ? nda.ifourierNd () : nda.fourierNd ());
        }
      else if (arg.iscomplex ())
        {
          ComplexNDArray cnda = arg.complex_array_value ();
 
          cnda.resize (dims, 0.0);
          retval = (type != 0 ? cnda.ifourierNd () : cnda.fourierNd ());
        }
      else
        err_wrong_type_arg (fcn, arg);
    }
 
  return retval;
}
 
DEFUN (fftn, args, ,
       doc: /* -*- texinfo -*-
@deftypefn  {} {@var{B} =} fftn (@var{A})
@deftypefnx {} {@var{B} =} fftn (@var{A}, @var{size})
Compute the N-dimensional discrete Fourier transform of @var{A} using
a Fast Fourier Transform (FFT) algorithm.
 
The optional vector argument @var{size} may be used specify the dimensions
of the array to be used.  If an element of @var{size} is smaller than the
corresponding dimension of @var{A}, then the dimension of @var{A} is
truncated prior to performing the FFT@.  Otherwise, if an element of
@var{size} is larger than the corresponding dimension then @var{A} is
resized and padded with zeros.
@seealso{ifftn, fft, fft2, fftw}
@end deftypefn */)
{
  return do_fftn (args, "fftn", 0);
}
 
/*
%!testif HAVE_FFTW <*65414>
%! sz = size (fftn (ones (2, 0, 3)));
%! assert (sz, [2, 0, 3]);
 
%!testif HAVE_FFTW <*65414>
%! sz = size (fftn (ones (5, 4, 3), [2, 0, 3]));
%! assert (sz, [2, 0, 3]);
*/
 
DEFUN (ifftn, args, ,
       doc: /* -*- texinfo -*-
@deftypefn  {} {@var{A} =} ifftn (@var{B})
@deftypefnx {} {@var{A} =} ifftn (@var{B}, @var{size})
Compute the inverse N-dimensional discrete Fourier transform of @var{B}
using a Fast Fourier Transform (FFT) algorithm.
 
The optional vector argument @var{size} may be used specify the dimensions
of the array to be used.  If an element of @var{size} is smaller than the
corresponding dimension of @var{B}, then the dimension of @var{B} is
truncated prior to performing the inverse FFT@.  Otherwise, if an element of
@var{size} is larger than the corresponding dimension then @var{B} is
resized and padded with zeros.
@seealso{fftn, ifft, ifft2, fftw}
@end deftypefn */)
{
  return do_fftn (args, "ifftn", 1);
}
 
/*
%!testif HAVE_FFTW <*65414>
%! sz = size (ifftn (ones (2, 0, 3)));
%! assert (sz, [2, 0, 3]);
 
%!testif HAVE_FFTW <*65414>
%! sz = size (ifftn (ones (5, 4, 3), [2, 0, 3]));
%! assert (sz, [2, 0, 3]);
*/
 
OCTAVE_END_NAMESPACE(octave)