The subspace method was initially used in linear feature extraction and data compression . it can compress vector data to energy concentrative axis and map data from high dimension space to low dimension space 子空间方法最初是线性特征抽取和数据压缩的产物，其作用是将矢量形式给出的数据压缩到能量集中的主轴上，实现数据从高维空间向低维空间映射。
