nnspe.m

最新的HHT时频分析程序By Huang and Wu

function [nt,tscale,fscale]=nnspe(data,t0,t1,fres,tres,fw0,fw1,tw0,tw1,ifmethod,normmethod,nfilter,lscale)

% The function NNSPE generates an improved HHT or zero-crossing spectrum of data (or LOG of data) data(n,k)
% in time-frequency (or time-log frequency) space, where n specifies the length of time series, and 
% k is the number of IMF components.
%
% NNSPE compute the Hilbert-Huang Spectrum of energy.
%
% Calling sequence-
%   [nt,tscale,fscale] = nnspe(data[, t0][, t1][, fres][, tres]
%                                  [, fw0][, fw1][,tw0][, tw1]
%                                  [, ifmethod][, normmethod][,nfilter][,lscale]) 
%
% Input-
%	  data        - 2-D input data(n,k) that specifies IMFs
%	  t0          - true start time
%	  t1          - true end time
%	  fres        - frequency resolution
%	  tres        - time resolution
%	  fw0         - minimum frequency
%	  fw1         - maximum frequency
%	  tw0         - minimum time for zooming
%	  tw1         - maximum time for zooming, if no zooming, tw0=t0, tw1=t1
%	  ifmethod    - nstantaneous frequency method, options: 'hilbert','hilbt','acos','zc','quad'
%	  normmethod  - normalization method, options: 'none','hilbert','spline','linear','pchip'
%	  nfilter     - number of points to filter by median
%
% Output-
%	  nt          - 2-D matrix that specifies the spectrum
%	  tscale      - vector that specifies the time axis values
%	  fscale      - vector that specifies the frequency axis values
%
% All arguments are required, WITHOUT default values.
%
% Ifmethod options:
%    'hilbert' :use Hilbert transform (function FAH )
%                  normalization of input data recommended but not required
%    'acos'    :use arccosine method (function FAACOS )
%		               normalization of input data required
%    'zc'      :use Generalized Zero-Crossing method (function FAZ )
%                  normalization of input data not recommended
%    'quad'    :use quadrature method (function calcqf),
%                  normalization of input data required
%    'hilbtm'  :use Hilbert transform, but hilbtm.m is used instead of the standard hilbert.m
%
% Normmethod options:
%    'none'	   :no normalization, recommended for 'zc' option
%    'spline'	 :spline normalization, recommended for 'hilbert' and 'acos' options
%               not recommended for Ensemble EMD method due to the possible overshot
%    'hilbert' (default) :Hilbert amplitude normalization, recommended when using Ensemble EMD method
%                this method is chosen as default because since 2008, EEMD will be mainly used
%    'linear'  :linear normalization, recommended for normalization when
%               using Ensemble EMD
%    'pchip'   :cubic hermite spline normalization, recommended for normalization when
%               using Ensemble EMD
%
% To display the output, use
%	   img(tscale,fscale,nt)
%	or
%	   contour(tscale,fscale,nt)
%	or
%    imagesc(tscale,fscale,nt);axis xy
%
% Non MATLAB Library routines used in the function are: FA, NSPPLOT.
%
 
% Kenneth Arnold (NASA GSFC)	    	Summer, 2003 Initial
%	(Based on work by Z. Shen (JHU) July, 2 1995.)
% Jelena Marshak (NASA GSFC)		March 17, 2004 Modified
%					(Added the LOG scale option.) 
%
% Xianyao Chen, September, 2008
%   nnspe is update version of nnsp, some options for ifmethod and normmethod are added, 
%      default values for the input parameters are removed.
%   nnspe calculates the HH spectrum of energy.
%   The countpart of nnspe is nnpsa, which calculate the spectrum of amplitude.
%