说明：  关于2dpca是否比传统的pca强，这一两年来，争论比较大，这篇国内的论文对这个问题提出了自己的看法。觉得不错，推荐！
(2dpca than on the traditional pca strong in the last couple of years, more controversial, This domestic paper on the issue put forward their views. Think it's good, recommended!)