function [a,phi,f] = spectra (x,fs)
%-----------------------------------------------------------------------
% Usage:       [a,phi,f] = spectra (x,fs)
%
% Description: Compute the amplitude and phase spectra of a 
%              discrete-time signal.
%
% Inputs:      x = n by 1 vector containing the discrete-time signal 
%              f = sampling frequency in Hz
%
% Outputs:     a   = n by 1 vector containing magnitude spectrum of x
%              phi = n by 1 vector containing phase spectrum of x in
%                    degrees
%              f   = n by 1 vector containing evaluation frequencies
%                    f(k) = (k-1)*fs/n
%-----------------------------------------------------------------------

   chkvec (x,1,'spectra');
   y = dft (x,1);
   a = abs (y);
   n = length(x);
   phi = zeros (n,1);
   f = (fs/n)*[0 : n-1]';
   for i = 1 : n
      if a(i) > eps
         phi(i) = (180/pi)*atan2(imag(y(i)),real(y(i)));
      else
         phi(i) = 0;
      end
   end
%-----------------------------------------------------------------------