% Problem # 16 (or Phillips' Function)
% Range of initial points: -3 <= x <= 3
% Global maxima: x=1.590717100915575
% f(x)=-7.515924153082323
% Coded by: Ali R. Alroomi | Last Update: 06 July 2015 | www.al-roomi.org
 
clear
clc
warning off
 
xmin=-3;
xmax=3;
R=100000; % steps resolution
x=xmin:(xmax-xmin)/R:xmax;
 
for i=1:length(x)
    f(i)=-2*(x(i)-3)^2-exp(x(i)^2/2);
end
 
plot(x,f,'r','LineWidth',2);grid;set(gca,'FontSize',12);
xlabel('x','FontName','Times','FontSize',20,'FontAngle','italic');
ylabel('f(x)','FontName','Times','FontSize',20,'FontAngle','italic');