说明：  用埃特金插值法依据N个已知数据点计算函数值 输入 n--已知数据点的个数N-1 x--已知数据点第一坐标的N维列向量
(Using Etkin interpolation method to calculate the number of N- known data points based on N known data points N dimension vector of the first coordinate of known data points)