Daniel@0: function h = draw_ellipse(x, c, outline_color, fill_color)
Daniel@0: % DRAW_ELLIPSE(x, c, outline_color, fill_color)
Daniel@0: %   Draws ellipses at centers x with covariance matrix c.
Daniel@0: %   x is a matrix of columns.  c is a positive definite matrix.
Daniel@0: %   outline_color and fill_color are optional.
Daniel@0: 
Daniel@0: n = 40;					% resolution
Daniel@0: radians = [0:(2*pi)/(n-1):2*pi];
Daniel@0: unitC = [sin(radians); cos(radians)];
Daniel@0: r = chol(c)';
Daniel@0: 
Daniel@0: if nargin < 3
Daniel@0:   outline_color = 'g';
Daniel@0: end
Daniel@0: 
Daniel@0: h = [];
Daniel@0: for i=1:cols(x)
Daniel@0:   y = r*unitC + repmat(x(:, i), 1, n);
Daniel@0:   if nargin < 4
Daniel@0:     h = [h line(y(1,:), y(2,:), 'Color', outline_color)];
Daniel@0:   else
Daniel@0:     h = [h fill(y(1,:), y(2,:), fill_color, 'EdgeColor', outline_color)];
Daniel@0:   end
Daniel@0: end