function [tfr,t,f] = tfrpage(x,t,N,trace);%TFRPAGE Page time-frequency distribution.%	[TFR,T,F]=TFRPAGE(X,T,N,TRACE) computes the Page distribution%	of a discrete-time signal X, %	or the cross Page representation between two signals. % %	X     : signal if auto-Page, or [X1,X2] if cross-Page.%	T     : time instant(s).%	N     : number of frequency bins  (default : length(X)).%	TRACE : if nonzero, the progression of the algorithm is shown%	                                  (default : 0).%	TFR   : time-frequency representation. When called without %               output arguments, TFRPAGE runs TFRQVIEW.%	F     : vector of normalized frequencies.%%	Example :%	 sig=fmlin(128,0.1,0.4); tfrpage(sig);% %	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 == 1), t=1:xrow; N=xrow; trace=0;elseif (nargin == 2), N=xrow; trace=0;elseif (nargin == 3), 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 (rem(log(N)/log(2),1)~=0), fprintf('For a faster computation, N should be a power of two\n');end; tfr= zeros (N,tcol) ;  if trace, disp('Page distribution'); end;for icol=1:tcol, ti=t(icol); tau=-min([N-ti,xrow-ti]):(ti-1); indices=rem(N+tau,N)+1; if trace, disprog(icol,tcol,10); end; tfr(indices,icol)= x(ti,1)*conj(x(ti-tau,xcol));end; if trace, fprintf('\n'); end;tfr= real(fft(tfr)); if (nargout==0), tfrqview(tfr,x,t,'tfrpage');elseif (nargout==3), f=fftshift((-N/2:N/2-1)/N)';end;