本人读取了数据文件,数据格式如下:
| date | a | b | c | 
| 2007-10-11 | -0.01256 | 0.025882916 | 0.02048 | 
| 2007-10-12 | 0.030873 | -0.018261084 | 0.042354 | 
| 2007-10-15 | -0.00857 | 0.026954916 | -0.03022 | 
| 2007-10-16 | 0.006848 | 0.036104916 | 0.009777 | 
| 2007-10-18 | -0.03234 | -0.041157084 | -0.05837 | 
| 2007-10-23 | 0.017852 | 0.053446916 | 0.047513 | 
| 2007-10-24 | -0.01309 | 0.011258916 | 0.013373 | 
| 2007-10-25 | -0.0022 | -0.042522084 | -0.03824 | 
| 2007-10-31 | 0.020654 | 0.001018916 | 0.036414 | 
| 2007-11-1 | -0.02041 | 0.011250916 | -0.00912 | 
| 2007-11-2 | -0.0391 | -0.021854084 | -0.0642 | 
请问使用何种函数,声明这是一个基于date为时间刻度(时间有间隔)的多元时间序列?谢谢大家!!