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%% Zero Freq. Centered Lorentzian  %% 
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define zfc_fit(lo,hi,par)
{
   variable a,f,al,ah,l;
 
   al = _A(lo);
   ah = _A(hi);
   f = par[1];
   
   a = par[0]^2 * PI/2./f;

   l = a*f/(al-ah) *  ( atan(al/f) - atan(ah/f) );

   l = reverse(l);

   return l;
}

add_slang_function("zfc",["norm [rms]","f [Hz]"]);

%% The below functions provide the parameter default values
%% The first function, is a subroutine that I call for *every* 
%% S-lang fit function default setup.

private define param_default_structure(value,freeze,pmin,pmax,
                                             hmin,hmax,pstep,prstep)
{
   variable param_def = struct{value, freeze, min, max,
                               hard_min, hard_max, step, relstep};
   param_def.value=value;
   param_def.freeze=freeze;
   param_def.min=pmin;
   param_def.max=pmax;
   param_def.hard_min=hmin;
   param_def.hard_max=hmax;
   param_def.step=pstep;
   param_def.relstep=prstep;
   return param_def;
}

define zfc_defaults(i)
{
   switch(i)
   {case 0:
      return param_default_structure(0.1,0,0.,1.e8,-1.e16,1.e16,1.e-3,1.e-3);
   }
   {case 1:
      return param_default_structure(1,0,1.e-6,1.e3,0,1.e16,1.e-3,1.e-3);
   }
}

set_param_default_hook("zfc","zfc_defaults");