function [Hw,f]=fr_resp(h,K,fs)
%% FR_RESP  Computes the samples of the frequency response (i.e., DFT)
%%          for an input sequence.  The user can specify number of
%%          points and a sample frequency. 
%%
%%   Usage: 
%%     [Hw,f]=fr_resp(h,K,fs)
%%
%%   Variables:
%%       h = sequence
%%       K = number of points desired [OPTIONAL - default = length(h)]
%%      fs = sampling frequency (Hz)  [OPTIONAL - no default]
%%
%%      Hw = samples of the frequency response of h
%%       f = frequency vector to plot against
%%              - if fs not specified, then f is [-pi,pi)
%%              - if fs specified, then f is in Hz
%%

%%  File     :  fr_resp.m
%%  Author   :  Kathleen E. Wage
%%  Date     :  August 22, 1998
%--------------------------------------------------------------------
%%%% Set up defaults

if nargin<2
  K=length(h);
  fscale=1;
elseif nargin<3
  fscale=1;
else			% If fs specified, then set up scale factor
  fscale=fs/(2*pi);	%  to return analog frequencies (Hz)
end
%--------------------------------------------------------------------
%%%% Compute the frequency response

Hw=fft(h,K);
%--------------------------------------------------------------------
%%%% Compute the frequency vector and reorganize frequency components
%%%%  so they are from [-pi,pi)

w=(2*pi/K)*[ 0:(K-1) ]';
mid=ceil(K/2)+1;
w(mid:K)=w(mid:K)-2*pi;   	% move [pi,2pi) to [-pi,0)

w=fftshift(w);
Hw=fftshift(Hw);                % move negative freq components

f=fscale*w;			% Scale frequency axis
%--------------------------------------------------------------------

return;