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