说明：  里面有用MATLAB自编的几个数值计算方面的几个程序，有拉格朗日多项式插值法，高斯消去法求解方程组，最小二乘法拟合，复合梯形公式求解数值积分
(Some Useful MATLAB self inside the numerical calculation of the number of procedures, Lagrange polynomial interpolation method, Gaussian elimination method for solving equations, least squares fitting, composite trapezoidal formula for numerical integration)