说明：  用高斯列主元消元法解下列线性方程组 高斯消元求解一些系数矩阵中含有极小数的情况下，会产生巨大的舍入误差，导致算法失效。一个简单而有效的改进方法是每次在进行将当前列中元素的消成0的运算时，选择当前列j对应的行(j to n)中绝对值较大的一个数作为主元行，这样，误差就会减小很多
(PCA with out Gaussian elimination method solution of the following system of linear equations to solve a number of Gauss elimination coefficient matrix contains a very small number of cases, it can have an enormous round-off errors, leading to algorithm failure. A simple and effective way to improve in carrying out elements of the current column to 0 of consumer computing, the choice of the current column j corresponds to the line (j to n) in a larger absolute number of firms as a principal, In this way, a lot of errors will be reduced)