我希望能够使用Kalman回归算法对一个价格数据流进行递归式的预测,使用kf.filter_update()方法,但是我无法让它正常工作。以下是问题的示例代码:
数据集(即数据流):
DateTime CAT DOG
2015-01-02 09:01:00, 1471.24, 9868.76
2015-01-02 09:02:00, 1471.75, 9877.75
2015-01-02 09:03:00, 1471.81, 9867.70
2015-01-02 09:04:00, 1471.59, 9849.03
2015-01-02 09:05:00, 1471.45, 9840.15
2015-01-02 09:06:00, 1471.16, 9852.71
2015-01-02 09:07:00, 1471.30, 9860.24
2015-01-02 09:08:00, 1471.39, 9862.94
数据被读入 Pandas 数据框中,以下代码模拟流式传输,通过对数据框进行迭代来实现:
df = pd.read_csv('data.txt')
df.dropna(inplace=True)
history = {}
history["spread"] = []
history["state_means"] = []
history["state_covs"] = []
for idx, row in df.iterrows():
if idx == 0: # Initialize the Kalman filter
delta = 1e-9
trans_cov = delta / (1 - delta) * np.eye(2)
obs_mat = np.vstack([df.iloc[0].CAT, np.ones(df.iloc[0].CAT.shape)]).T[:, np.newaxis]
kf = KalmanFilter(n_dim_obs=1, n_dim_state=2,
initial_state_mean=np.zeros(2),
initial_state_covariance=np.ones((2, 2)),
transition_matrices=np.eye(2),
observation_matrices=obs_mat,
observation_covariance=1.0,
transition_covariance=trans_cov)
state_means, state_covs = kf.filter(np.asarray(df.iloc[0].DOG))
history["state_means"], history["state_covs"] = state_means, state_covs
slope=state_means[:, 0]
print "SLOPE", slope
else:
state_means, state_covs = kf.filter_update(history["state_means"][-1], history["state_covs"][-1], observation = np.asarray(df.iloc[idx].DOG))
history["state_means"].append(state_means)
history["state_covs"].append(state_covs)
slope=state_means[:, 0]
print "SLOPE", slope
卡尔曼滤波器已正确初始化,我得到了第一个回归系数,但随后的更新引发了异常:
Traceback (most recent call last):
SLOPE [ 6.70319125]
File "C:/Users/.../KalmanUpdate_example.py", line 50, in <module>
KalmanOnline(df)
File "C:/Users/.../KalmanUpdate_example.py", line 43, in KalmanOnline
state_means, state_covs = kf.filter_update(history["state_means"][-1], history["state_covs"][-1], observation = np.asarray(df.iloc[idx].DOG))
File "C:\Python27\Lib\site-packages\pykalman\standard.py", line 1253, in filter_update
2, "observation_matrix"
File "C:\Python27\Lib\site-packages\pykalman\standard.py", line 38, in _arg_or_default
+ ' You must specify it manually.') % (name,)
ValueError: observation_matrix is not constant for all time. You must specify it manually.
Process finished with exit code 1
直觉上来讲,似乎需要观察矩阵(它在初始步骤中提供,但在更新步骤中没有提供),但我无法弄清如何正确设置它。非常感谢任何反馈。