% ELLIPSOID Draws an ellipsoid.
% P = ELIPSOID_SHELL(Q,q,N) generates (N+1) vector in a cell so that
% points over axis P{n} has computed.
%
% P = ELLIPSOID_SHELL(Q,q) use N = 20.
%
% ELLIPSOID_SHELL(...) with no output arguments graph the ellipsoid
% as a SURFACE and return nothing.
%
% The ellipsoidal data is generated using the equation:
%
% (x-q)'*inv(Q)*(x-q) = 1
%
% where Q corresponding to the positive definite symmetric
% matrix. If dim(q)>3 there are no plot.
%
% Example:
%
% P = ellipsoid_shell(diag([3;5;4]));
%
% q = [3;2;1];
% Q = [8.5 2.9 1.5; 2.9 3.8 1; 1.5 1 .5];
% ellipsoid_shell(Q,q,30);
%
% See also sphere, cylinder.