矩阵基本运算
a = np.array([[1, 2], [3, 4]])
b = np.array([[1, 0], [0, 1]])
c = np.array([[2, 0], [0, 2]])
d = np.array([[2, 1], [1, 2]])
a + b
a - b
a * c
a @ c
a / d
a ** d
广播机制
a1 = np.array([[1,2,3], [4,5,6], [7,8,9]])
a2 = np.array([1,2,3])
b1 = np.array([-1, 0, 1])
b2 = np.array([[3], [6], [9]])
b3 = np.array([[1], [2], [3]])
a1 / np.array([9])
a1 * b1
a1 / b2
a1 * b3
a2 @ b3
