%function y = rotate(x,axis,angle)
%rotate vector x about axis by angle
% x, y, axis are vextors (3X1 arrays), angle is real scalar
function y = rotate(x,axis,angle)
   q  = rotator(axis,angle);
   qc = quatconj(q);
   qx = quaternion(x);
   qx = quatmul(q ,qx);
   qx = quatmul(qx,qc);
   y  = qx(2:4)';
   

 
