1 %% Copyright (C) 2006 Peter V. Lanspeary <pvl@mecheng.adelaide.edu.au>
3 %% This program is free software; you can redistribute it and/or modify it under
4 %% the terms of the GNU General Public License as published by the Free Software
5 %% Foundation; either version 3 of the License, or (at your option) any later
8 %% This program is distributed in the hope that it will be useful, but WITHOUT
9 %% ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 %% FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
13 %% You should have received a copy of the GNU General Public License along with
14 %% this program; if not, see <http://www.gnu.org/licenses/>.
17 %% [psd,f_out] = pyulear(x,poles,freq,Fs,range,method,plot_type)
19 %% Calculates a Yule-Walker autoregressive (all-pole) model of the data "x"
20 %% and computes the power spectrum of the model. This is a wrapper for
21 %% functions "aryule" and "ar_psd" which perform the argument checking.
22 %% See "help aryule" and "help ar_psd" for further details.
25 %% All but the first two arguments are optional and may be empty.
26 %% x %% [vector] sampled data
28 %% poles %% [integer scalar] required number of poles of the AR model
30 %% freq %% [real vector] frequencies at which power spectral density
32 %% %% [integer scalar] number of uniformly distributed frequency
33 %% %% values at which spectral density is calculated.
36 %% Fs %% [real scalar] sampling frequency (Hertz) [default=1]
39 %% CONTROL-STRING ARGUMENTS -- each of these arguments is a character string.
40 %% Control-string arguments can be in any order after the other arguments.
43 %% range %% 'half', 'onesided' : frequency range of the spectrum is
44 %% %% from zero up to but not including sample_f/2. Power
45 %% %% from negative frequencies is added to the positive
46 %% %% side of the spectrum.
47 %% %% 'whole', 'twosided' : frequency range of the spectrum is
48 %% %% -sample_f/2 to sample_f/2, with negative frequencies
49 %% %% stored in "wrap around" order after the positive
50 %% %% frequencies; e.g. frequencies for a 10-point 'twosided'
51 %% %% spectrum are 0 0.1 0.2 0.3 0.4 0.5 -0.4 -0.3 -0.2 -0.1
52 %% %% 'shift', 'centerdc' : same as 'whole' but with the first half
53 %% %% of the spectrum swapped with second half to put the
54 %% %% zero-frequency value in the middle. (See "help
55 %% %% fftshift". If "freq" is vector, 'shift' is ignored.
56 %% %% If model coefficients "ar_coeffs" are real, the default
57 %% %% range is 'half', otherwise default range is 'whole'.
59 %% method %% 'fft': use FFT to calculate power spectrum.
60 %% %% 'poly': calculate power spectrum as a polynomial of 1/z
61 %% %% N.B. this argument is ignored if the "freq" argument is a
62 %% %% vector. The default is 'poly' unless the "freq"
63 %% %% argument is an integer power of 2.
65 %% plot_type %% 'plot', 'semilogx', 'semilogy', 'loglog', 'squared' or 'db':
66 %% %% specifies the type of plot. The default is 'plot', which
67 %% %% means linear-linear axes. 'squared' is the same as 'plot'.
68 %% %% 'dB' plots "10*log10(psd)". This argument is ignored and a
69 %% %% spectrum is not plotted if the caller requires a returned
73 %% If return values are not required by the caller, the spectrum
74 %% is plotted and nothing is returned.
75 %% psd %% [real vector] power-spectrum estimate
76 %% f_out %% [real vector] frequency values
79 %% This function is a wrapper for aryule and ar_psd.
80 %% See "help aryule", "help ar_psd".
82 function [psd,f_out]=pyulear(x,poles,varargin)
85 error( 'pburg: need at least 2 args. Use "help pburg"' );
88 [ar_coeffs,residual,k]=aryule(x,poles);
90 ar_psd(ar_coeffs,residual,varargin{:});
92 psd = ar_psd(ar_coeffs,residual,varargin{:});
94 [psd,f_out] = ar_psd(ar_coeffs,residual,varargin{:});
100 %! rand('seed',2038014164);
101 %! a = [ 1.0 -1.6216505 1.1102795 -0.4621741 0.2075552 -0.018756746 ];
102 %! signal = detrend(filter(0.70181,a,rand(1,16384)));
103 %! % frequency shift by modulating with exp(j.omega.t)
104 %! skewed = signal.*exp(2*pi*i*2/25*[1:16384]);
107 %! pyulear(signal,3,[],Fs);
108 %! disp( 'Results from this demo should be nearly the same as pburg demo' );
109 %! input('Onesided 3-pole spectrum. Press ENTER', 's' );
110 %! pyulear(signal,4,[],Fs,'whole');
111 %! input('Twosided 4-pole spectrum of same data. Press ENTER', 's' );
112 %! pyulear(signal,5,128,Fs,'shift', 'semilogy');
113 %! input('Twosided, centred zero-frequency, 5-pole. Press ENTER', 's' );
114 %! pyulear(skewed,7,128,Fs,'shift','semilogy');
115 %! input('Complex data, frequency-shifted. Press ENTER', 's' );
116 %! user_freq=[-0.2:0.02:0.2]*Fs;
117 %! pyulear(skewed,7,user_freq,Fs,'semilogy');
118 %! input('User-specified frequency values. Press ENTER', 's' );