% function [K] = area2P (A0,A1,A2,Kmax);
%
% Function araa2P calculates parameter of the P (proportional) controller:
%
% u = K*e
%
% from the measured areas of the process A0 to A2 (A0 is the process steady-state gain).
% The parameter Kmax represents the highest allowed open-loop gain K*A0 


function [K] = area2P (A0,A1,A2,Kmax);

Num = 2*A0*A2 - A1*A1;			% Numerator
Den = 2*A0*(A1*A1-A0*A2);		% Denominator

if (Num == 0)
   K = 0;
elseif (Den == 0)
   if (A0 ~= 0)
      K = Kmax/A0;
   else
      K = Kmax;
   end;
else
   K = Num/Den;
end;

Tmp = K*A0;							% Nominal gain

if (Tmp > Kmax) | (Tmp < 0)
   K = Kmax/A0;
end;