function [maximum,err]=quad2(pts,checkpt,location)
%QUAD2  Quadraticly interpolates three points to find the maximum value.
%   QUAD2(PTS,CHECKPT,LOCATION)
%   The second argument, CHECKPT, is for estimation of the error 
%   in the interpolated maximum. 

%   Copyright 1990-2000 The MathWorks, Inc.
%   $Revision: 1.9 $  $Date: 2000/06/16 22:25:27 $

c=pts(1);
ab=[-1 0.5; 2 -0.5]*(pts(2:3)-c*ones(2,1));
stepmin=-ab(2)/(2*ab(1));
maximum=ab(1)*stepmin^2+ab(2)*stepmin+c;
if nargin>1
    if location==0
        checkpt2=-abc(1)+abc(2)-abc(3)+d;
    else
        checkpt2=64*abc(1)+16*abc(2)+4*abc(3)+d;
    end
    err=checkpt-checkpt2;
end
