scipy.interpolate.lagrange

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拉格朗日插值法是scipy库中常用的插值方法。

官网定义如下：

scipy.interpolate.lagrange(x, w)[source]Return a Lagrange interpolating polynomial.Given two 1-D arrays x and w, returns the Lagrange interpolating polynomial through the points (x, w).Warning: This implementation is numerically unstable. Do not expect to be able to use more than about 20 points even if they are chosen optimally.Parameters:x : array_likex represents the x-coordinates of a set of datapoints.w : array_likew represents the y-coordinates of a set of datapoints, i.e. f(x).Returns:lagrange : numpy.poly1d instanceThe Lagrange interpolating polynomial.

其参数为两个一维数组，分别代表坐标的x值和y值，输出是多项式。可以直接用了计算插值。

例如：

x=[100,200,300,400]

y=[10,20,30,40]

f=lagrange(x,y)

求在500处的插值f(500)得到49.999999999999837，符号我们的数据

Warning: This implementation is numerically unstable. Do not expect to be able to use more than about 20 points even if they are chosen optimally.

这方法不是很稳定，所有输入的数据点最好不要超过20个

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