/usr/share/octave/packages/nan-3.1.4/nanfft.m is in octave-nan 3.1.4-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 | function [Y,N,N2] = nanfft(X,N,DIM);
% NANFFT calculates the Fourier-Transform of X for data with missing values.
% NANFFT is the same as FFT but X can contain missing values encoded with NaN.
% NaN's are skipped, NaN do not result in a NaN output.
%
% Y = NANFFT(X)
% Y = NANFFT(X,N)
% Y = NANFFT(X,[],DIM)
%
% [Y,N] = NANFFT(...)
% returns the number of valid samples N
%
%
% WARNING: missing values can introduce aliasing - causing unintended results.
% Moreover, the behavior of bandpass and highpass filters in case of missing values
% is not fully understood, and might contain some pitfalls.
%
% see also: FFT, XCORR, NANCONV, NANFILTER
% $Id$
% Copyright (C) 2005,2011 by Alois Schloegl <alois.schloegl@gmail.com>
% This function is part of the NaN-toolbox available at
% http://pub.ist.ac.at/~schloegl/matlab/NaN/ and
% http://octave.svn.sourceforge.net/viewvc/octave/trunk/octave-forge/extra/NaN/inst/
% This program 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.
%
% This program 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 this program; if not, write to the Free Software
% Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
warning('NANFFT is experimental. For more details see HELP NANFFT');
NX = isnan(X);
X(NX) = 0;
if nargin==1,
Y = fft(X);
N2 = sum(1-NX); %
N = fft(NX);
elseif nargin==2,
Y = fft(X,N);
N2 = sum(1-NX);
N = fft(NX);
elseif nargin==3,
Y = fft(X,N,DIM);
N2 = sum(1-NX,DIM); %
N = fft(NX,N,DIM);
end;
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