tfrpmh.m

matlab时间序列分析工具箱

function [tfr,t,f] = tfrpmh(x,t,N,h,trace);
%TFRPMH  Pseudo Margenau-Hill time-frequency distribution.
%       [TFR,T,F]=TFRPMH(X,T,N,H,TRACE) computes the Pseudo Margenau-Hill  
%       distribution of a discrete-time signal X, or the
%       cross Pseudo Margenau-Hill representation between two signals. 
% 
%       X     : signal if auto-PMH, or [X1,X2] if cross-PMH.
%       T     : time instant(s)          (default : 1:length(X)).
%       N     : number of frequency bins (default : length(X)).
%       H     : frequency smoothing window, H(0) being forced to 1
%                                        (default : Hamming(N/4)). 
%       TRACE : if nonzero, the progression of the algorithm is shown
%                                        (default : 0).
%       TFR   : time-frequency representation. When called without 
%               output arguments, TFRPMH runs TFRQVIEW.
%       F     : vector of normalized frequencies.
%
%       Example :
%        sig=fmlin(128,0.1,0.4); t=1:128; 
%        h=window(63,'Kaiser'); tfrpmh(sig,t,128,h,1);
% 
%       See also all the time-frequency representations listed in
%        the file CONTENTS (TFR*)

%       F. Auger, May-August 1994, July 1995.
%	Copyright (c) 1996 by CNRS (France).
%
%	------------------- CONFIDENTIAL PROGRAM -------------------- 
%	This program can not be used without the authorization of its
%	author(s). For any comment or bug report, please send e-mail to 
%	[e-mail]

[xrow,xcol] = size(x);
if (nargin < 1),
 error('At least 1 parameter is required');
elseif nargin<=2,
 N=xrow;
end;

hlength=floor(N/4);
hlength=hlength+1-rem(hlength,2);

if (nargin == 1),
 t=1:xrow; h = window(hlength); trace=0;
elseif (nargin == 2 | nargin == 3),
 h = window(hlength); trace = 0;
elseif (nargin == 4),
 trace = 0;
end;

if (N<0),
 error('N must be greater than zero');
end;
[trow,tcol] = size(t);
if (xcol==0)|(xcol>2),
 error('X must have one or two columns');
elseif (trow~=1),
 error('T must only have one row'); 
elseif (2^nextpow2(N)~=N), %(rem(log(N)/log(2),1)~=0),
 fprintf('For a faster computation, N should be a power of two\n');
end; 

[hrow,hcol]=size(h); Lh=(hrow-1)/2; h=h/h(Lh+1);
if (hcol~=1)|(rem(hrow,2)==0),
 error('H must be a smoothing window with odd length');
end;

tfr= zeros (N,tcol) ;  
if trace, disp('Pseudo Margenau-Hill distribution'); end;
for icol=1:tcol,
 ti= t(icol); tau=-min([round(N/2)-1,Lh,xrow-ti]):min([round(N/2)-1,Lh,ti-1]);
 indices= rem(N+tau,N)+1;
 if trace, disprog(icol,tcol,10); end;
 tfr(indices,icol)=h(Lh+1+tau).*x(ti,1).*conj(x(ti-tau,xcol));
end; 
if trace, fprintf('\n'); end;
tfr= real(fft(tfr)); 

if (nargout<=1),
 tfrqview(tfr,x,t,'tfrpmh',h);
elseif (nargout==3),
 f=fftshift((-N/2:N/2-1)/N)';
end;