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下面是一个使用加权最小二乘法、极大似然估计和奇异值分解法求解Lee-Carter模型参数估计的示例代码:
```python
import numpy as np
from scipy.optimize import minimize
from scipy.linalg import svd
# 定义Lee-Carter模型的目标函数
def lee_carter_objective(params, age, year, log_mortality, weights):
alpha, beta, k = params
log_mortality_hat = alpha + beta * age + k * year
residuals = log_mortality - log_mortality_hat
weighted_residuals = weights * residuals
return np.sum(weighted_residuals**2)
# 定义奇异值分解法求解Lee-Carter模型的参数估计
def lee_carter_svd(age, year, log_mortality, weights):
X = np.column_stack((np.ones_like(age), age, year))
W = np.diag(np.sqrt(weights))
X_tilde = W @ X
y_tilde = W @ log_mortality
U, s, Vt = svd(X_tilde, full_matrices=False)
V = Vt.T
S_inv = np.diag(1 / s)
beta_hat = V @ S_inv @ U.T @ y_tilde
alpha_hat = beta_hat[0]
beta_hat = beta_hat[1]
k_hat = beta_hat[2]
return alpha_hat, beta_hat, k_hat
# 生成示例数据
age = np.array([50, 51, 52, 53, 54, 55])
year = np.array([2000, 2001, 2002, 2003, 2004, 2005])
log_mortality = np.array([0.01, 0.02, 0.03, 0.04, 0.05, 0.06])
weights = np.array([1, 2, 3, 4, 5, 6])
# 使用加权最小二乘法求解Lee-Carter模型的参数估计
initial_params = np.array([0, 0, 0])
result = minimize(lee_carter_objective, initial_params, args=(age, year, log_mortality, weights))
alpha_hat, beta_hat, k_hat = result.x
# 使用奇异值分解法求解Lee-Carter模型的参数估计
alpha_hat_svd, beta_hat_svd, k_hat_svd = lee_carter_svd(age, year, log_mortality, weights)
print("加权最小二乘法估计结果:")
print("alpha_hat =", alpha_hat)
print("beta_hat =", beta_hat)
print("k_hat =", k_hat)
print("奇异值分解法估计结果:")
print("alpha_hat_svd =", alpha_hat_svd)
print("beta_hat_svd =", beta_hat_svd)
print("k_hat_svd =", k_hat_svd)
```
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