import numpy as np

print(np.cov([1,1,1,1,1]))              # 方差
print(np.std([1,1,1,1,1]))              # 标准差
x = [-2.1, -1,  4.3]
y = [3,  1.1,  0.12]
X = np.vstack((x,y))                    # 垂直堆叠矩阵
print(X)
print(np.cov(X))                        # 协方差
print(np.cov(x, y))
print(np.std(X))                        # 标准差
print(np.std(X, axis=1))
print(np.cov(x))                        # 方差