polar-decomp-3by3 contains a MATLAB function polar_quaternion for
computing the polar decomposition of a real 3-by-3 matrix.
This decomposition has the form A = Q*H, where Q is orthogonal and H is
symmetric positive semidefinite.
The underlying algorithm is developed in the open-access paper
N. J. Higham and V. Noferini. "An algorithm to compute the polar decomposition of a $3 \times 3$ matrix". Numer. Algorithms, 73(2):349-369, 2016.
The function test.m tests that the code is working correctly.
The codes have been developed under MATLAB 2016a and have been tested with MATLAB 2016b.
See license.txt for licensing information.