提供了拉格朗日插值 一次多项式拟合 指数拟合三种计算方式。是使用picturebox作图的好例子，其中test.xls是一个4点的数据文件-Provides three method of calculation, there are the Lagrange interpolation polynomial fitting exponential fitting . Is a good example of using picturebox drawing, test.xls is a 4 p