Calculate inverse of quaternion
n = quatinv(q)
n = quatinv(q) calculates the inverse, n, for a given quaternion, q. Input q is an m-by-4 matrix containing m quaternions. n returns an m-by-4 matrix of inverses. Each element of q must be a real number. Additionally, q has its scalar number as the first column.
The quaternion has the form of
The quaternion inverse has the form of
 Stevens, Brian L., Frank L. Lewis, Aircraft Control and Simulation, Wiley–Interscience, 2nd Edition.