如何在Python中为股票价格数据添加趋势线？

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
from scipy.signal import savgol_filter

# 假设已经有了一个包含股票价格数据的DataFrame对象，其中日期列为"date"，价格列为"close"
# 以下为示例数据
data = pd.DataFrame({
    'date': ['2022-01-01', '2022-01-02', '2022-01-03', '2022-01-04', '2022-01-05', '2022-01-06'],
    'close': [100, 110, 120, 130, 125, 140]
})

# 使用Savitzky-Golay滤波器平滑数据
window_length = 5  # 滑动窗口长度
polyorder = 2  # 多项式拟合阶数
smoothed = savgol_filter(data['close'], window_length, polyorder)

# 计算趋势线
trend = np.gradient(smoothed)  # 计算一阶导数，表示趋势

# 绘制原始价格数据
plt.plot(data['date'], data['close'], label='Price')

# 绘制趋势线
plt.plot(data['date'], trend, label='Trend')

# 添加图例和标题
plt.legend()
plt.title('Stock Price with Trend Line')

# 显示图形
plt.show()