function [a,b,az]=errell2(C)% ERRELL2  Computes 2D error ellipse from covariance matrix.%   Note: x & y represent north & south (opposite of%   normal MatLab convention).  Non-vectorized.  See also%   ERRELL3.% Version: 24 Jan 96% Useage:  [a,b,az]=errell2(C)% Input:   C  - covariance matrix (2D)% Output:  a  - major semi-axis of error ellipse%          b  - minor semi-axis of error elilpse%          az - azimuth of major axis (rad)if nargin~=1  error('Wrong number of input arguments');endif (nargout~=3)  error('Wrong number of output arguments');end[V,D]=eig(C);     % Eigenvalues & vectorsd=diag(D);inda=find(max(d)==d);indb=find(min(d)==d);a=sqrt(d(inda(1)));b=sqrt(d(indb(1)));az=atan2(V(2,inda(1)),V(1,inda(1)));