/usr/share/octave/packages/signal-1.3.2/__power.m is in octave-signal 1.3.2-1+b1.
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 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 | ## Copyright (C) 1999 Paul Kienzle <pkienzle@users.sf.net>
##
## 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, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {[@var{P}, @var{w}] =} __power (@var{b}, @var{a})
## @deftypefnx {Function File} {[@dots{}] =} __power (@var{b}, @var{a}, @var{nfft})
## @deftypefnx {Function File} {[@dots{}] =} __power (@var{b}, @var{a}, @var{nfft}, @var{Fs})
## @deftypefnx {Function File} {[@dots{}] =} __power (@var{b}, @var{a}, @var{nfft}, @var{Fs}, @var{range})
## @deftypefnx {Function File} {[@dots{}] =} __power (@var{b}, @var{a}, @var{nfft}, @var{Fs}, @var{range}, @var{units})
## @deftypefnx {Function File} {} __power (@dots{})
##
## Plot the power spectrum of the given ARMA model.
##
## b, a: filter coefficients (b=numerator, a=denominator)
## nfft is number of points at which to sample the power spectrum
## Fs is the sampling frequency of x
## range is 'half' (default) or 'whole'
## units is 'squared' or 'db' (default)
## range and units may be specified any time after the filter, in either
## order
##
## Returns P, the magnitude vector, and w, the frequencies at which it
## is sampled. If there are no return values requested, then plot the power
## spectrum and don't return anything.
## @end deftypefn
## FIXME: consider folding this into freqz --- just one more parameter to
## distinguish between 'linear', 'log', 'logsquared' and 'squared'
function varargout = __power (b, a, varargin)
if (nargin < 2 || nargin > 6) print_usage; endif
nfft = [];
Fs = [];
range = [];
range_fact = 1.0;
units = [];
pos = 0;
for i=1:length(varargin)
arg = varargin{i};
if strcmp(arg, 'squared') || strcmp(arg, 'db')
units = arg;
elseif strcmp(arg, 'whole')
range = arg;
range_fact = 1.0;
elseif strcmp(arg, 'half')
range = arg;
range_fact = 2.0;
elseif ischar(arg)
usage(usagestr);
elseif pos == 0
nfft = arg;
pos++;
elseif pos == 1
Fs = arg;
pos++;
else
usage(usagestr);
endif
endfor
if isempty(nfft); nfft = 256; endif
if isempty(Fs); Fs = 2; endif
if isempty(range)
range = 'half';
range_fact = 2.0;
endif
[P, w] = freqz(b, a, nfft, range, Fs);
P = (range_fact/Fs)*(P.*conj(P));
if nargout == 0,
if strcmp(units, 'squared')
plot(w, P, ";;");
else
plot(w, 10.0*log10(abs(P)), ";;");
endif
endif
if nargout >= 1, varargout{1} = P; endif
if nargout >= 2, varargout{2} = w; endif
endfunction
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