Take the tour ×  Looking on Internet, I mostly found this
definition:  Given quantities on a cyclic domain D, first
rescale the domain to [0;2$\pi$[, then, find $z_n$ the point on
the unit circle corresponding to the $n$th value, and compute
the average by:  $$z_m = \sum_{n=1}^N z_n$$  The average angle
is then $\theta_m = \arg z_m$ and to obtain the average value
you scale back to your original domain D.  I must say, I have
problems with this definition. For simplicity, I will use
oriented angles in degree for my examples (i.e. D = [0;360[).
With this formula, having angles -90, 90 and 40 will give 40 as
mean angle, when I would expect 13.33 as an answer (i.e.
(90-90+40)/3).  For my own problems, I usually use:  $$v_m =
\mathop{\rm arg\,min}_{v\in D} \sum_{n=1}^{N} d(v_n,v)^2$$
Where $d(x,y)$ is the distance in the cyclic domain, and $\{v_1,
v_2, \ldots, v_n\}$ is the set of cyclic data I want to average
of.  It has the advantage to work the same way whatever the
domain (replace D by a non-cyclic domain and