MATLAB里的pburg函数可以直接调用吗？如果不能直接调用那么应该怎么定义呢？
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可以直接调用，输入help pburg会有帮助说明。以下摘取
usage:
[psd,f_out] = pburg(x,poles,freq,Fs,range,method,plot_type,criterion)
Calculate Burg maximum-entropy power spectral density.
The functions "arburg" and "ar_psd" do all the work.
See "help arburg" and "help ar_psd" for further details.
ARGUMENTS:
All but the first two arguments are optional and may be empty.
x %% [vector] sampled data
poles %% [integer scalar] required number of poles of the AR model
freq %% [real vector] frequencies at which power spectral density
%% is calculated
%% [integer scalar] number of uniformly distributed frequency
%% values at which spectral density is calculated.
%% [default=256]
Fs %% [real scalar] sampling frequency (Hertz) [default=1]
CONTROL-STRING ARGUMENTS -- each of these arguments is a character string.
Control-string arguments can be in any order after the other arguments.
range %% 'half', 'onesided' : frequency range of the spectrum is
%% from zero up to but not including sample_f/2. Power
%% from negative frequencies is added to the positive
%% side of the spectrum.
%% 'whole', 'twosided' : frequency range of the spectrum is
%% -sample_f/2 to sample_f/2, with negative frequencies
%% stored in "wrap around" order after the positive
%% frequencies; e.g. frequencies for a 10-point 'twosided'
%% spectrum are 0 0.1 0.2 0.3 0.4 0.5 -0.4 -0.3 -0.2 -0.1
%% 'shift', 'centerdc' : same as 'whole' but with the first half
%% of the spectrum swapped with second half to put the
%% zero-frequency value in the middle. (See "help
%% fftshift". If "freq" is vector, 'shift' is ignored.
%% If model coefficients "ar_coeffs" are real, the default
%% range is 'half', otherwise default range is 'whole'.
method %% 'fft': use FFT to calculate power spectral density.
%% 'poly': calculate spectral density as a polynomial of 1/z
%% N.B. this argument is ignored if the "freq" argument is a
%% vector. The default is 'poly' unless the "freq"
%% argument is an integer power of 2.
plot_type %% 'plot', 'semilogx', 'semilogy', 'loglog', 'squared' or 'db':
%% specifies the type of plot. The default is 'plot', which
%% means linear-linear axes. 'squared' is the same as 'plot'.
%% 'dB' plots "10*log10(psd)". This argument is ignored and a
%% spectrum is not plotted if the caller requires a returned
%% value.
criterion %% [optional string arg] model-selection criterion. Limits
%% the number of poles so that spurious poles are not
%% added when the whitened data has no more information
%% in it (see Kay & Marple, 1981). Recognized values are
%% 'AKICc' -- approximate corrected Kullback information
%% criterion (recommended),
%% 'KIC' -- Kullback information criterion
%% 'AICc' -- corrected Akaike information criterion
%% 'AIC' -- Akaike information criterion
%% 'FPE' -- final prediction error" criterion
%% The default is to NOT use a model-selection criterion
RETURNED VALUES:
If return values are not required by the caller, the spectrum
is plotted and nothing is returned.
psd %% [real vector] power-spectral density estimate
f_out %% [real vector] frequency values
HINTS
This function is a wrapper for arburg and ar_psd.
See "help arburg", "help ar_psd".
