说明：  最小二乘法曲线拟合的经典算法，做过特征数检验，只需调用fit，文件中其他函数被fit调用，其中个输入输出变量均以给出详细说明。
(least squares curve fitting classic algorithms, the number of tests done, just call fit, the paper other function to be fit Call, 000 input and output variables were presented in detail.)