matthiasm@8: function h=plotgauss2d_old(mu, Sigma, plot_cross)
matthiasm@8: % PLOTGAUSS2D Plot a 2D Gaussian as an ellipse with optional cross hairs
matthiasm@8: % h=plotgauss2(mu, Sigma)
matthiasm@8: % 
matthiasm@8: % h=plotgauss2(mu, Sigma, 1) also plots the major and minor axes
matthiasm@8: %
matthiasm@8: % Example
matthiasm@8: % clf; S=[2 1; 1 2]; plotgauss2d([0;0], S, 1); axis equal
matthiasm@8: 
matthiasm@8: if nargin < 3, plot_cross = 0; end
matthiasm@8: [V,D]=eig(Sigma);
matthiasm@8: lam1 = D(1,1);
matthiasm@8: lam2 = D(2,2);
matthiasm@8: v1 = V(:,1);
matthiasm@8: v2 = V(:,2);
matthiasm@8: %assert(approxeq(v1' * v2, 0))
matthiasm@8: if v1(1)==0
matthiasm@8:   theta = 0; % horizontal
matthiasm@8: else
matthiasm@8:   theta = atan(v1(2)/v1(1));
matthiasm@8: end
matthiasm@8: a = sqrt(lam1);
matthiasm@8: b = sqrt(lam2);
matthiasm@8: h=plot_ellipse(mu(1), mu(2), theta, a,b);
matthiasm@8: 
matthiasm@8: if plot_cross
matthiasm@8:   mu = mu(:);
matthiasm@8:   held = ishold;
matthiasm@8:   hold on
matthiasm@8:   minor1 = mu-a*v1; minor2 = mu+a*v1;
matthiasm@8:   hminor = line([minor1(1) minor2(1)], [minor1(2) minor2(2)]);
matthiasm@8:   
matthiasm@8:   major1 = mu-b*v2; major2 = mu+b*v2;
matthiasm@8:   hmajor = line([major1(1) major2(1)], [major1(2) major2(2)]);
matthiasm@8:   %set(hmajor,'color','r')
matthiasm@8:   if ~held
matthiasm@8:     hold off
matthiasm@8:   end
matthiasm@8: end
matthiasm@8: