Directional data arise in many applications where observations are naturally represented as unit vectors or as observations on the surface of a unit hypersphere. In this context, statistical depth functions provide a center--outward ordering of the data. This work aims at proposing the use of a local notion of data depth function to be applied in the DD-plot (Depth vs. Depth plot) to classify directional data. The proposed method is investigated through an extensive simulation study and two real-data examples.

翻译：方向数据广泛存在于许多应用领域，其中观测值自然地表示为单位向量或单位超球面上的观测点。在此背景下，统计深度函数提供了数据从中心到外部的排序。本研究旨在提出一种局部数据深度函数的概念，并将其应用于DD图（深度-深度图）中对方向数据进行分类。通过广泛的模拟研究和两个实际数据案例，对所提出的方法进行了深入探讨。