I was looking at an article in which I found this :
. I tried to reproduce this figure but I did not find the same thing at all. I am wondering whether this would actually be the contour plot of $\log p(x,y)$. Still, when I plot $\log p(x,y)$ for $-15 \leq x \leq 15$ and $-15 \leq y \leq 15$, I do not have the same figure.
In MATLAB, I used :
x=linspace(-15,15);
y=linspace(-15,15);
[X,Y]=meshgrid(x,y);
myfun = @(X,Y) exp( -X.^2 -Y.^2 - 0.25.*((X.^2 - Y.^2).^2) );
Z=myfun(X,Y);
figure;
contour(X,Y,Z); %not normalized
I=quad2d(@(X,Y) myfun(X,Y),-15,15,-15,15);
figure;
contour(X,Y,Z./I); %normalized
What am I getting wrong ?