[90d51d]: inst / __power.m Maximize Restore History

Download this file

__power.m    97 lines (86 with data), 3.1 kB

 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