python numpy的var std cov研究

import numpy as np
 
# 构建测试数据，均值为10
sc = [9.7, 10, 10.3, 9.7, 10, 10.3, 9.7, 10, 10.3]
 
# 输出均值为10.0
print(np.mean(sc))
 
# 输出var, 即(0.09 + 0 + 0.09 + 0.09 + 0 + 0.09 + 0.09 + 0 + 0.09) = 0.54, 再0.54 / 9=0.06, 输出0.06
print(np.var(sc))
 
# 相当于0.06 开根号
print(np.std(sc))
 
# 0.54 / 8 = 0.0675
print(np.cov(sc))

10.0
0.06
0.244948974278
0.06750000000000032