function [gd,fnorm]=sgrpdlay(x,fnorm);%SGRPDLAY Group delay estimation of a signal.%	[GD,FNORM]=SGRPDLAY(X,FNORM) estimates the group delay of%	signal X at the normalized frequency(ies) FNORM.%%	X     : signal in the time-domain.%	FNORM : normalized frequency. By default, FNORM is a %               linearly spaced vector between -0.5 and 0.5 with%               length(X) elements.%	GD    : computed group delay. When GD equals zero, it means that%	 	the estimation of the group delay for this frequency was %		outside the interval [1 xrow], and therefore meaningless.%%	Example : %	 N=128; x=amgauss(N,64,30).*fmlin(N,0.1,0.4);%	 fnorm=0.1:0.04:0.38; gd=sgrpdlay(x,fnorm); %	 t=2:N-1; instf=instfreq(x,t);%	 plot(t,instf,gd,fnorm); axis([1 N 0 0.5]); %	F. Auger, March 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 if (nargin == 0), error('At least one parameter required');end;[xrow,xcol] = size(x); if (xcol~=1), error('x must have only one column');end;Ex=mean(abs(x).^2); Threshold=1.0e-6;if (nargin==1),  Num=fft(x .* (1:xrow)'); Den=fft(x); ratio=(real(Num./Den) .* (real(Num./Den)>=1) .* (real(Num./Den)<=xrow+3)); gd=fftshift(ratio); if (nargout==2),  if (rem(xrow,2)==0),   L=xrow/2;   fnorm=(-L:L-1)/xrow;  else   L=(xrow-1)/2;   fnorm=(-L:L)/xrow;  end; end;elseif (nargin==2), [fnormrow,fnormcol] = size(fnorm); if (fnormrow~=1),  error('FNORM must have only one row'); end; expo=exp(-j*2.0*pi*fnorm'*(0:xrow-1)); Num=expo*(x .* (1:xrow)'); Den=expo*x;  gd=(real(Num./Den) .* (real(Num./Den)>=1) .* (real(Num./Den)<=xrow+3));end;