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−% RESP returns the complex response of the pz object.
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−%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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−%
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−% DESCRIPTION: RESP returns the complex response of the pz object. The
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−%              response is computed assuming that object represents a pole.
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−%              If the object represents a zero, just take the inverse of
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−%              the returned response: 1./r.
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−%
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−% CALL:        [f,r] = resp(p, f);          % compute response for vector f
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−%              [f,r] = resp(p, f1, f2, nf); % compute response from f1 to f2
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−%                                           % in nf steps.
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−%              [f,r] = resp(p, f1, f2, nf, scale); % compute response from f1 to f2
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−%                                                  % in nf steps using scale ['lin' or 'log'].
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−%              [f,r] = resp(p);             % compute response
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−%
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−% REMARK:      This is just a helper function. This function should only be
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−%              called from class functions.
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−%
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−% VERSION:     $Id: resp.m,v 1.9 2011/02/18 16:48:54 ingo Exp $
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−%
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−%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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−
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−function [f,r] = resp(varargin)
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−
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−  %%% Input objects checks
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−  if nargin < 1
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−    error('### incorrect number of inputs.')
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−  end
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−
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−  %%% look at inputs
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−  p = varargin{1};
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−  if ~isa(p, 'pz')
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−    error('### first argument should be a pz object.');
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−  end
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−
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−  %%% decide whether we modify the pz-object, or create a new one.
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−  p = copy(p, nargout);
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−
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−  %%% Now look at the pole
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−  f0 = p.f;
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−  Q  = p.q;
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−
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−  %%% Define frequency vector
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−  f = [];
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−
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−  if nargin == 1
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−    f1 = f0/10;
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−    f2 = f0*10;
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−    nf = 1000;
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−    scale = 'lin';
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−  elseif nargin == 2
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−    f = varargin{2};
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−  elseif nargin == 4
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−    f1 = varargin{2};
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−    f2 = varargin{3};
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−    nf = varargin{4};
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−    scale = 'lin';
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−  elseif nargin == 5
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−    f1    = varargin{2};
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−    f2    = varargin{3};
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−    nf    = varargin{4};
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−    scale = varargin{5};
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−  else
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−    error('### incorrect number of inputs.');
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−  end
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−
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−  %%% Build f if we need it
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−  if isempty(f)
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−    switch lower(scale)
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−      case 'lin'
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−        f   = linspace(f1, f2, nf);
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−      case 'log'
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−        f = logspace(log10(f1), log10(f2), nf);
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−    end
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−  end
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−
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−
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−  %%% Now compute the response
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−  if Q>=0.5
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−    re = 1 - (f.^2./f0^2);
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−    im = f ./ (f0*Q);
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−    r = 1./complex(re, im);
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−  else
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−    re = 1;
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−    im = f./f0;
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−    r = 1./complex(re, im);
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−  end
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−end
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−