Hi again everyone,

the first milestones proposed here have been implemented:

- sampling from the hypersphere

- directional sample statistics (direction mean and mean resultant length)

I would like to propose to further add the most commonly used analogue of the normal distribution on the hypersphere: the von Mises-Fisher distribution (vMF). A reference implementations for sampling from it is available in geomstats and fitting and evaluating pdf/logpdf should not be too difficult to implement by ourselves.

Having worked with directional data a lot, I have seen many people struggle with these distributions. I do not think that all kinds of spherical distributions should become part of SciPy, but the vMF is so fundamental that it would be very valuable to the general community.