Question: 海天味业2021年03月17日至2021年12月08日的下行偏差的值是？（默认目标收益率为0；无需年化）使用不复权价格，写出指标公式，搜集原始数据，计算得出答案，保留四位小数。注意列出原始数据和关键计算过程。
Formula: DD = \sqrt{1 / N * \sum_{t=1}^{N} min(r_t - rf, 0)^2}
Data:
date,close
2021-03-16,151.95
2021-03-17,152.87
2021-03-18,157.27
2021-03-19,152.05
2021-03-22,151.66
2021-03-23,148.5
2021-03-24,146.51
2021-03-25,147.91
2021-03-26,150.45
2021-03-29,152.06
2021-03-30,157.58
2021-03-31,159.8
2021-04-01,165.42
2021-04-02,170.4
2021-04-06,167.33
2021-04-07,170.23
2021-04-08,175.4
2021-04-09,171.79
2021-04-12,168.85
2021-04-13,170.6
2021-04-14,169.63
2021-04-15,169.25
2021-04-16,167.0
2021-04-19,169.24
2021-04-20,167.96
2021-04-21,167.85
2021-04-22,163.6
2021-04-23,170.8
2021-04-26,162.01
2021-04-27,163.33
2021-04-28,161.5
2021-04-29,166.0
2021-04-30,169.5
2021-05-06,164.99
2021-05-07,159.09
2021-05-10,159.6
2021-05-11,168.05
2021-05-12,168.68
2021-05-13,170.6
2021-05-14,173.57
2021-05-17,136.45
2021-05-18,134.67
2021-05-19,132.96
2021-05-20,133.0
2021-05-21,131.59
2021-05-24,132.3
2021-05-25,138.75
2021-05-26,137.1
2021-05-27,138.01
2021-05-28,135.83
2021-05-31,137.26
2021-06-01,138.96
2021-06-02,138.02
2021-06-03,136.8
2021-06-04,137.42
2021-06-07,136.13
2021-06-08,135.0
2021-06-09,135.8
2021-06-10,136.16
2021-06-11,134.68
2021-06-15,131.45
2021-06-16,133.9
2021-06-17,131.57
2021-06-18,129.5
2021-06-21,129.74
2021-06-22,130.92
2021-06-23,130.17
2021-06-24,130.01
2021-06-25,132.5
2021-06-28,132.48
2021-06-29,129.33
2021-06-30,128.95
2021-07-01,132.0
2021-07-02,126.24
2021-07-05,121.15
2021-07-06,117.59
2021-07-07,116.96
2021-07-08,117.34
2021-07-09,113.9
2021-07-12,116.87
2021-07-13,122.98
2021-07-14,124.82
2021-07-15,128.49
2021-07-16,123.11
2021-07-19,122.58
2021-07-20,123.86
2021-07-21,119.16
2021-07-22,119.6
2021-07-23,118.39
2021-07-26,116.04
2021-07-27,113.1
2021-07-28,112.7
2021-07-29,114.48
2021-07-30,114.64
2021-08-02,117.79
2021-08-03,119.08
2021-08-04,116.03
2021-08-05,117.35
2021-08-06,114.79
2021-08-09,121.06
2021-08-10,122.7
2021-08-11,119.56
2021-08-12,116.02
2021-08-13,115.68
2021-08-16,115.5
2021-08-17,111.9
2021-08-18,111.45
2021-08-19,110.42
2021-08-20,105.45
2021-08-23,104.98
2021-08-24,109.78
2021-08-25,109.29
2021-08-26,106.75
2021-08-27,106.09
2021-08-30,105.53
2021-08-31,94.98
2021-09-01,93.05
2021-09-02,89.8
2021-09-03,90.07
2021-09-06,92.02
2021-09-07,90.24
2021-09-08,90.75
2021-09-09,90.0
2021-09-10,90.77
2021-09-13,88.96
2021-09-14,88.18
2021-09-15,86.32
2021-09-16,89.06
2021-09-17,89.1
2021-09-22,87.08
2021-09-23,91.58
2021-09-24,100.74
2021-09-27,106.63
2021-09-28,107.67
2021-09-29,109.75
2021-09-30,110.0
2021-10-08,112.0
2021-10-11,109.92
2021-10-12,114.0
2021-10-13,113.55
2021-10-14,112.38
2021-10-15,114.67
2021-10-18,112.55
2021-10-19,115.8
2021-10-20,117.68
2021-10-21,117.0
2021-10-22,121.8
2021-10-25,118.45
2021-10-26,116.22
2021-10-27,116.25
2021-10-28,116.41
2021-10-29,117.02
2021-11-01,112.89
2021-11-02,120.0
2021-11-03,118.32
2021-11-04,123.52
2021-11-05,123.46
2021-11-08,120.05
2021-11-09,119.9
2021-11-10,117.54
2021-11-11,117.89
2021-11-12,116.4
2021-11-15,121.86
2021-11-16,121.46
2021-11-17,120.71
2021-11-18,118.98
2021-11-19,119.9
2021-11-22,118.08
2021-11-23,117.37
2021-11-24,116.38
2021-11-25,115.38
2021-11-26,114.66
2021-11-29,113.5
2021-11-30,112.3
2021-12-01,113.68
2021-12-02,112.7
2021-12-03,111.55
2021-12-06,109.86
2021-12-07,112.7
2021-12-08,112.8

Indicator data:
Answer: 0.0228