文件的读取、拼接，最小二乘拟合，曲线拟合，并做散点图(Reading and splicing of files, fitting of least squares, fitting of curves, and making scatter plot)

最小二乘拟合曲线；系统建模与辨识课程中所用到的两个最基础的程序(Least squares fitting curve,The two most basic programs used in the system modeling and identification course)