Directional statistics

Summary

Directional statistics is the part of statistics whose observations are directions, angles or rotations. Such data live on the circle, on a sphere or on other manifolds, not on a line, so the usual mean and variance can mislead. Means are taken of unit vectors instead of angles, and models such as the von Mises–Fisher distribution replace the normal distribution. Applications include wind directions, animal navigation, times of day and orientations of rocks.