function [b,a] = parmeq(R,r)
%  parmeq --> Graphic equalizer based on parametric filters.
%
%  <Synopsis>
%    [b,a] = parmeq(R,r)
%
%  <Description>
%    The graphic equalizer consists of a cascade of N second order
%    parametric filters. R and r are N-vectors used to design
%    the parametric filters. If R(i) < r(i), the i'th filter will
%    be a notch filter, otherwise it will be a peak filter. The gain
%    of the peak (notch) is determined by the closeness of r(i) and R(i),
%    and the width of the peak (notch) is determined by the closeness
%    of r(i) and R(i) to the unit circle.
%
%  <See Also>
%    parmfilt --> Second-order parametric filter design.

%  <Revision>
%    Peter S.K. Hansen, IMM, Technical University of Denmark
%
%    Last revised: March 20, 2000
%-----------------------------------------------------------------------

N = length(R);
b = 1; a = 1;
w0 = pi/(2*N):(pi/N):pi;

for (i=1:N)
  [bi,ai] = parmfilt(w0(i),R(i),r(i));

  a = conv(a,ai);
  b = conv(b,bi);
end

%-----------------------------------------------------------------------
% End of function parmeq
%-----------------------------------------------------------------------