说明：  LDA空间降维程序，此程序通计算数据的特征值和特征向量，再通过矩阵相乘，从而达到降维的目的。
(LDA space dimension reduction procedure, this procedure pass computing the eigenvalues ​ ​ and eigenvectors of the data, and then through the matrix multiplication, so as to achieve the purpose of dimension reduction.)