% Figure of Banana Function

%  NUMERICAL METHODS: Matlab Programs
% (c) 2007 by Xie Liling
%  Complementary Software to accompany the textbook:
%  Information and Computing Science: A Laboratory Course

figure
x1=[-2:0.125:2]';
x2=[-1:0.125:3]';
[x1,x2]=meshgrid(x1',x2');
meshd=100*(x2-x1.^2).^2+(1-x1).^2;
mesh(meshd)
view(-40.5,20.4)
xlabel('x_1');
ylabel('x_2');
zlabel('f(x)');

% Contour of Banana Function
figure
conts=exp(3:20);
contour(x1,x2,meshd,conts,'k:')

% 3D Contour of Banana Function
figure
[x1,x2]=meshgrid(0.5:0.01:1.5);
z=100*(x2-x1.^2).^2+(1-x1).^2;
contour3(x1,x2,z,100),zlim([0,310])
hold on
plot3(1,1,0,'ro')