function [ax,az,inc]=errell3(C)% ERRELL3  Computes 3D error ellipsoid from covariance matrix.%   Semi-axes lengths, azimuth, inclinations are ordered%   from smallest to largest.  Note: x & y represent north%   & south (opposite of normal MatLab convention).%   Non-vectorized for multiple stations.  See also ERRELL2.% Version: 18 Jan 96% Useage:  [ax,az,inc]=errell3(C)% Input:   C  - covariance matrix (3D)% Output:  a  - vector of semi-axes lengths%          az - vector of semi-axes azimuths (rad)%          inc- vector of semi-axes inclinations (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 & vectors[d,ind]=sort(diag(D));   % Sort eigenvaluesV=V(:,ind);              % and eigenvectors%d=flipud(d);     % flip order to (max to min)%V=flipud(V);ax=sqrt(d);az=atan2(V(2,:)',V(1,:)');inc=asin(V(3,:)');