%
%  code3Mc.m -- 16 sept 02 -- djm
%
%  contour plotter

%  clear workspace & graphics

clear;  close all

%  set t & v grid matrices ("help meshgrid")

x = -5:0.05:5;  y = -5:0.05:5;
[xx,yy] = meshgrid(x,y);

%  calculate constant (matrix arithmetic, use , .* etc)

K = 0.5*(xx.^2 - yy.^2) + exp(-xx) - exp(yy);

%  plot tangent vectors ("help quiver") 

figure(1);  hold on
contour(x,y,K,[-8:2:8],'r')
contour(x,y,K,[0 0],'k')
axis([-5 5 -5 5])

%  label plot

title(['integral curves (prob 2.2.7)'])
xlabel('x-axis')
ylabel('y-axis')