--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m-toolbox/classes/@pz/resp.m	Wed Nov 23 19:22:13 2011 +0100
@@ -0,0 +1,89 @@
+% RESP returns the complex response of the pz object.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
+% DESCRIPTION: RESP returns the complex response of the pz object. The
+%              response is computed assuming that object represents a pole.
+%              If the object represents a zero, just take the inverse of
+%              the returned response: 1./r.
+%
+% CALL:        [f,r] = resp(p, f);          % compute response for vector f
+%              [f,r] = resp(p, f1, f2, nf); % compute response from f1 to f2
+%                                           % in nf steps.
+%              [f,r] = resp(p, f1, f2, nf, scale); % compute response from f1 to f2
+%                                                  % in nf steps using scale ['lin' or 'log'].
+%              [f,r] = resp(p);             % compute response
+%
+% REMARK:      This is just a helper function. This function should only be
+%              called from class functions.
+%
+% VERSION:     $Id: resp.m,v 1.9 2011/02/18 16:48:54 ingo Exp $
+%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+function [f,r] = resp(varargin)
+
+  %%% Input objects checks
+  if nargin < 1
+    error('### incorrect number of inputs.')
+  end
+
+  %%% look at inputs
+  p = varargin{1};
+  if ~isa(p, 'pz')
+    error('### first argument should be a pz object.');
+  end
+
+  %%% decide whether we modify the pz-object, or create a new one.
+  p = copy(p, nargout);
+
+  %%% Now look at the pole
+  f0 = p.f;
+  Q  = p.q;
+
+  %%% Define frequency vector
+  f = [];
+
+  if nargin == 1
+    f1 = f0/10;
+    f2 = f0*10;
+    nf = 1000;
+    scale = 'lin';
+  elseif nargin == 2
+    f = varargin{2};
+  elseif nargin == 4
+    f1 = varargin{2};
+    f2 = varargin{3};
+    nf = varargin{4};
+    scale = 'lin';
+  elseif nargin == 5
+    f1    = varargin{2};
+    f2    = varargin{3};
+    nf    = varargin{4};
+    scale = varargin{5};
+  else
+    error('### incorrect number of inputs.');
+  end
+
+  %%% Build f if we need it
+  if isempty(f)
+    switch lower(scale)
+      case 'lin'
+        f   = linspace(f1, f2, nf);
+      case 'log'
+        f = logspace(log10(f1), log10(f2), nf);
+    end
+  end
+
+
+  %%% Now compute the response
+  if Q>=0.5
+    re = 1 - (f.^2./f0^2);
+    im = f ./ (f0*Q);
+    r = 1./complex(re, im);
+  else
+    re = 1;
+    im = f./f0;
+    r = 1./complex(re, im);
+  end
+end
+