function Px = ev(x,p,M)
%EV	Frequency estimation using the eigenvector method
%--
%USAGE	Px = ev(x,p,M)
%
%	The input sequence x is assumed to consist of p complex
%	exponentials in white noise.  The frequencies of the
%	complex exponentials and the variance of the white noise
%	are estimated using the eigenvector method.  
%
%	x : input sequence
%	p : Number of complex exponential in x
%	M : Size of the autocorrelation matrix to use in
%	      estimating the complex exponential frequencies
%
%	The frequency estimates are found from the peaks of the
%	pseudospectrum Px.
%
%  see also PHD, MUSIC, and MIN_NORM
%
%---------------------------------------------------------------
% copyright 1996, by M.H. Hayes.  For use with the book 
% "Statistical Digital Signal Processing and Modeling"
% (John Wiley & Sons, 1996).
%---------------------------------------------------------------

   x   = x(:);
   if N<p+1, error('Specified size of R is too small'), end
   R = covar(x,N);
   [v,d]=eig(R);
   [y,i]=sort(diag(d));
   Px=0;
   for j=1:N-p
       Px=Px+abs(fft(v(:,i(j)),1024)).^2/abs(y(j));
       end;
   Px=-10*log10(Px);
   end;