function [Z] = gauss2d(x, y, mu, sigma)
%GAUSS2D Returns the two dimensional gaussian with the given properties. 
%
%  Usage: gauss2d(x,y,mu,sigma)
%   where
%     x : 1-d array of x values
%     y : 1-d array of y values
%    mu : [mu_x, mu_y]
% sigma : [sigma_x_squared, sigma_xy; sigma_yx; sigma_y_squared]
[X, Y] = meshgrid(x-mu(1), y-mu(2));
coef = 1/(2 * pi * sqrt(det(sigma)));
isig = inv(sigma);
Z = coef * exp(-0.5 * (X.*(X.*isig(1,1)+Y.*isig(1,2)) + (Y.*(X.*isig(2,1) + Y.*isig(2,2)))));


%
% Author:
%   Bill Baxter
%   Comp 235
%   October 13, 1995