Compass and accelerometer data -> Quaternion

Question

Do it yourself

Friends!

Given:
B - 3-dimensional vector of magnetic induction (obtained from a magnetometer)
a - acceleration vector (at rest = gravitational acceleration vector)

Find:
quaternion of rotation relative to the Earth ( NED - X=North, Y=East, Z=Down )
(well, or a matrix - it doesn’t matter)

At the moment I know that there are 5-10 algorithms for solving this problem - QUEST (QUaternion ESTimator), FQA (Factored Quaternion Algorithm), ESOQ (EStimator of the Optimal Quaternion), ESOQ -2, FOAM (Fast Optimal Attitude Matrix), there is still a solution via SVD (singular value decomposition)

The problem is that I can't find any implementation of any of these algorithms. Moreover, apparently, all of them were implemented only in matlab, but I can’t even find the matlab code. I am sure that determining the orientation in space relative to the Earth is a typical task for any driving/flying/floating things that you, dear subscribers of the DIY hub, do/did. It's strange how hard it is to find information.