wolffd@0: function h=plotgauss2d_old(mu, Sigma, plot_cross)
wolffd@0: % PLOTGAUSS2D Plot a 2D Gaussian as an ellipse with optional cross hairs
wolffd@0: % h=plotgauss2(mu, Sigma)
wolffd@0: % 
wolffd@0: % h=plotgauss2(mu, Sigma, 1) also plots the major and minor axes
wolffd@0: %
wolffd@0: % Example
wolffd@0: % clf; S=[2 1; 1 2]; plotgauss2d([0;0], S, 1); axis equal
wolffd@0: 
wolffd@0: if nargin < 3, plot_cross = 0; end
wolffd@0: [V,D]=eig(Sigma);
wolffd@0: lam1 = D(1,1);
wolffd@0: lam2 = D(2,2);
wolffd@0: v1 = V(:,1);
wolffd@0: v2 = V(:,2);
wolffd@0: %assert(approxeq(v1' * v2, 0))
wolffd@0: if v1(1)==0
wolffd@0:   theta = 0; % horizontal
wolffd@0: else
wolffd@0:   theta = atan(v1(2)/v1(1));
wolffd@0: end
wolffd@0: a = sqrt(lam1);
wolffd@0: b = sqrt(lam2);
wolffd@0: h=plot_ellipse(mu(1), mu(2), theta, a,b);
wolffd@0: 
wolffd@0: if plot_cross
wolffd@0:   mu = mu(:);
wolffd@0:   held = ishold;
wolffd@0:   hold on
wolffd@0:   minor1 = mu-a*v1; minor2 = mu+a*v1;
wolffd@0:   hminor = line([minor1(1) minor2(1)], [minor1(2) minor2(2)]);
wolffd@0:   
wolffd@0:   major1 = mu-b*v2; major2 = mu+b*v2;
wolffd@0:   hmajor = line([major1(1) major2(1)], [major1(2) major2(2)]);
wolffd@0:   %set(hmajor,'color','r')
wolffd@0:   if ~held
wolffd@0:     hold off
wolffd@0:   end
wolffd@0: end
wolffd@0: