If you have a normal-vector to a plane and want to plot 2 vectors in the plane you could do something like this:
n = [n_x,n_y,n_z]; % your normal-vector;
e_r = randn(1,3);e_r = e_r/norm(e_r); % randomly selected unit-vector;
% You should put in some checks for e_r being || to n here...
e1 = cross(n,e_r);
e1 = e1/norm(e1);
e2 = cross(n,e1);% and normalize
Then you have 2 perpendicular vectors in the plane. Plot with any of the arrow-functions you find on the file-exchange, I alternate between arrow3 and arrow
HTH
