doolittle

代码说明：

   1.n个节点分段Lagrange插值多项式； 2.使用格式y=lagrange(x0,y0,x,k)； 3.输入项x0为n维插值节点向量，y0为n维被插函数值向量； 4.x为m维插值点向量，k为分段插值多项式次数，不超过3，缺省为k=1； 5.输出y为插值点x处的函数值；( 1.n a sub-node Lagrange interpolation polynomial 2. The use of the format y = lagrange (x0, y0, x, k) 3. Input x0 of interpolation nodes for the n-dimensional vector, y0 for n-dimensional vector function to be inserted 4.x interpolation points for the m-dimensional vector, k is the number of sub-polynomial interpolation, not more than 3, the default for k = 1 5. output y for the interpolation points x Department of function )