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.%