该文件里面主要包含了一个学习文档，是详细的介绍了PCA的推导过程，以及学习PCA是为了什么，主要有什么目的，用于人脸图像有什么作用等，对于初学者是非常的有帮助的。-The document which consists mainly　a learning document, which is a detailed descr iption of the derivation of the PCA and learning the PCA is what, what is the main purpose for the human face images, such as what role, for beginners is very helpful.