1. Introduction
Many common data sets can be modeled by mixtures of fiats (i.e., affine subspaces). For example, feature vectors of different moving objects in a video sequence lie on different affine subspaces (see e.g., [14]), and similarly, images of different faces under different illuminating conditions are on different linear subspaces with each such subspace corresponding to a distinct face [1]. Such data give rise to the problem of hybrid linear modeling, i.e., modeling data by a mixture of fiats.