fa.m

最新的HHT时频分析程序By Huang and Wu

function [f,a] = fa(data,dt,ifmethod,normmethod,nfilter)

% The function FA computes a frequency and amplitude of data(n,k), where 
% n specifies the length of time series, and k is the number of IMFs.
% The user has a choice to choose the instantaneous frequency and
% normalization methods. Nature of the arcosine method suggests not 
% to use the latter to process the residue component.
% First 2 arguments are required. If not passed the rest is set to have 
% default values: the frequency and amplitude is calculated using Hilbert
% method with spline normalization and no smoothing of data.
%
% Calling sequence-
% [f,a] = fa(data,dt[,ifmethod][,normmethod][,nfilter])
%
% Input-
%	  data		  - 2-D matrix of IMF components
%	  dt		    - time increment per point
%	  ifmethod	- method of determining an instantaneous frequency (and amplitude)
%	  normmethod	- normalization method
%	  nfilter		- number of points to use for filter
% Output-
%	  f		    - 2-D matrix f(n,k) that specifies frequency
%	  a		    - 2-D matrix a(n,k) that specifies amplitude
%
% 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 (pchip.m), recommended for normalization when
%               using Ensemble EMD
%
% Non MATLAB Library routines used in the function are:
% 	FAACOS, FAH, FAZ,FAHT 
%	BLOCKNORMALIZE, SPLINENORMALIZE, HILBERTNORMALIZE, MEDIANFILTER.
 
% Kenneth Arnold (NASA GSFC)	Summer 2003, Initial
% Karin Blank (NASA GSFC)       5/17/05, edited to add Quad
%
% Xianyao Chen (RCADA, FIO)   Sep. 20, 2008
%   1. add 'linear' and 'hermite' options for the normalization
%      to avoid the overshot of 'spline' method when using Ensemble EMD,
%   2. the default normalization method is given as 'hilbert' for the case
%      of 'ifmethod' is 'hilbert'
%   3. the extra necessary spline normalization when using 'quad' ifmethod
%      is changed from splinenormalize to hermitenormalize