A type of cyclic data in which measurements are directions. Axial data occur when a data item has known orientation but its direction is not known—for example, an iron filing will align itself either way around in a magnetic field. In this case the effective orientations lie in a 180° range. To utilize the standard methods for cyclic data it is usual to double all the angles (subtracting 360° if required).
Subjects: Probability and Statistics.