function [tfr,t,f] = tfrstft(x,t,N,h,trace);%TFRSTFT Short time Fourier transform.%	[TFR,T,F]=TFRSTFT(X,T,N,H,TRACE) computes the short-time Fourier %	transform of a discrete-time signal X. % %	X     : signal.%	T     : time instant(s)          (default : 1:length(X)).%	N     : number of frequency bins (default : length(X)).%	H     : frequency smoothing window, H being normalized so as to%	        be  of unit energy.      (default : Hamming(N/4)). %	TRACE : if nonzero, the progression of the algorithm is shown%	                                 (default : 0).%	TFR   : time-frequency decomposition (complex values). The%	        frequency axis is graduated from -0.5 to 0.5.%	F     : vector of normalized frequencies.%%	Example :%	 sig=[fmconst(128,0.2);fmconst(128,0.4)]; tfr=tfrstft(sig);%	 subplot(211); imagesc(abs(tfr));%	 subplot(212); imagesc(angle(tfr));% %	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 %	f.auger@ieee.org [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~=1), error('X must have one column');elseif (trow~=1), error('T must only have one row'); elseif (2^nextpow2(N)~=N), fprintf('For a faster computation, N should be a power of two\n');end; [hrow,hcol]=size(h); Lh=(hrow-1)/2; if (hcol~=1)|(rem(hrow,2)==0), error('H must be a smoothing window with odd length');end;h=h/norm(h);tfr= zeros (N,tcol) ;  if trace, disp('Short-time Fourier transform'); end;for icol=1:tcol, ti= t(icol); tau=-min([round(N/2)-1,Lh,ti-1]):min([round(N/2)-1,Lh,xrow-ti]); indices= rem(N+tau,N)+1;  if trace, disprog(icol,tcol,10); end; tfr(indices,icol)=x(ti+tau,1).*conj(h(Lh+1+tau));end;tfr=fft(tfr); if trace, fprintf('\n'); end;if (nargout==0), tfrqview(abs(tfr).^2,x,t,'tfrstft',h);elseif (nargout==3), f=fftshift(0.5*(-N:N-1)/N)';end;