计算方法 | Lagrange 插值方法

很简单，先求l(x)，再乘y加起来求个和。

# data = eval(input("请输入数据:"))
data = [(0.4,-0.916291), (0.5,-0.693147), (0.6,-0.510826), (0.7,-0.356675)]
m = len(data)
l = [0 for i in range(m)]
x = 0.54
_sum = 0
# 求l表然后乘y的值
for i in range(m):
    up = 1
    down = 1
    for j in range(m):
        if j != i:
            up = up * (x - data[j][0])
            down = down * (data[i][0] - data[j][0])
    l[i] = up / down
    _sum += data[i][1] * l[i]
    
print(_sum)