ABSTRACT
This chapter gives an introductory description of statistical analysis of data where the observations are directions in ℝ2 or ℝ3. In biology, geology, and related fields of natural science, there are numerous examples of such data and, historically, these data have been the most important source of inspiration for the development of statistical models for directions. As examples of two-dimensional directional data, one may think of recordings of wind directions or current directions and registrations of directions of the flying patterns of birds, whereas measurements of directions of remanent magnetism in specimens of lava is an example of a three-dimensional directional data set.
