function Px = minvar(x,p)
%MINVAR	Spectrum estimation using the minimum variance method.
%----
%USAGE	Px = minvar(x,p) 
%
%	The spectrum of a process x is estimated using the minimum
%	variance method (sometimes called the maximum likelihood
%	method).
%
%	x  :  Input sequence
%	p  :  Order of the minimum variance estimate - for short
%		sequences, p is typically about length(x)/3
%
%	The spectrum estimate is returned in Px using a dB scale.
%
%---------------------------------------------------------------
% copyright 1996, by M.H. Hayes.  For use with the book 
% "Statistical Digital Signal Processing and Modeling"
% (John Wiley & Sons, 1996).
%---------------------------------------------------------------
%
   x = x(:);
   R = covar(x,p);
   [v,d]=eig(R);
   U = diag(inv(abs(d)+eps));
   V  = abs(fft(v,1024)).^2;
   Px = 10*log10(p)-10*log10(V*U);
   end;

