% Example 5.1a (Physics 330)

%*********************************************************
% Define the arrays x and y
% Warning: don't make the step size too small or you will
% kill the system
%*********************************************************

clear;close all;
x=-1:.1:1;y=0:.1:1.5;

%*********************************************************
% Use meshgrid to convert these 1-d arrays into 2-d matrices of
% x and y values over the plane
%*********************************************************

[X,Y]=meshgrid(x,y);

%*********************************************************
% Get F(x,y) by using F(X,Y).  Note the use of .* with X and Y
% rather than with x and y
%*********************************************************

F=(2-cos(pi*X)).*exp(Y);

%*********************************************************
% Note that this function is uphill in y between x=-1 and x=1
% and has a valley at x=0
%*********************************************************

surf(X,Y,F);
xlabel('x');
ylabel('y');