cheby2

% Generate an Chebyshev type II filter with Rs dB of stop band attenuation.
% 
% [b, a] = cheby2(n, Rs, Wc)
%    low pass filter with cutoff pi*Wc radians
%
% [b, a] = cheby2(n, Rs, Wc, 'high')
%    high pass filter with cutoff pi*Wc radians
%
% [b, a] = cheby2(n, Rs, [Wl, Wh])
%    band pass filter with edges pi*Wl and pi*Wh radians
%
% [b, a] = cheby2(n, Rs, [Wl, Wh], 'stop')
%    band reject filter with edges pi*Wl and pi*Wh radians
%
% [z, p, g] = cheby2(...)
%    return filter as zero-pole-gain rather than coefficients of the
%    numerator and denominator polynomials.
%
% [...] = cheby2(...,'s')
%     return a Laplace space filter, W can be larger than 1.
% 
% [a,b,c,d] = cheby2(...)
%  return  state-space matrices 
% 
% References: 
%
% Parks & Burrus (1987). Digital Filter Design. New York:
% John Wiley & Sons, Inc.