It returns an unsigned unite quaternion in S^3 (the four-dimensional sphere) from a 3 \times 3 rotation matrix on SO(3).
A rotation matrix in SO(3).
Firstly construct a system of linear equations by equating the corresponding components of the theoretical rotation matrix proposed by Prentice (1986), and given a rotation matrix. Finally, the system of linear equations are solved by following the tricks mentioned in second reference here in order to achieve numerical accuracy to get quaternion values.
A unsigned unite quaternion.
R implementation and documentation: Anamul Sajib <email@example.com>
Prentice,M. J. (1986). Orientation statistics without parametric assumptions.Journal of the Royal Statistical Society. Series B: Methodological 48(2). //http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/index.htm
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