拉格朗日插值法--python实现

直观地理解拉格朗日插值法：如何直观地理解拉格朗日插值法？ - 知乎 (zhihu.com)

import pandas as pd
from scipy.interpolate import lagrange #导入拉格朗日函数
import numpy as np
import matplotlib.pyplot as plt


mydata = pd.read_excel('数据清洗.xlsx', sheet_name='sales_')

mydata1 = mydata.copy()

for i in range(len(mydata1)):
    if pd.isna(mydata1.loc[i, 'sales']) == True:
        if i < 5:
            y = mydata1['sales'][list(range(0, i)) + list(range(i+1, i+6))]
        elif i > len(mydata1) - 6:
            y = mydata1['sales'][list(range(i-5, i)) + list(range(i+1, len(mydata1)))]
        else:
            y = mydata1['sales'][list(range(i-5, i)) + list(range(i+1, i+6))]
        y = y[y.notnull()]  # 取出空值
        mydata1.loc[i, 'sales'] = lagrange(y.index, list(y))(i)
mydata1

补充阅读：

没有完美的数据插补法，只有最适合的 - 知乎 (zhihu.com)