>>> a = np.array([1, 2, 3])
>>> a
array([1, 2, 3])
>>> a.transpose()
array([1, 2, 3])
>>> a.dot(a.transpose())
14
现在将其强制为列向量:
>>> a.shape = (3,1)
>>> a
array([[1],
[2],
[3]])
>>> a.transpose()
array([[1, 2, 3]])
>>> a.dot(a.transpose())
array([[1, 2, 3],
[2, 4, 6],
[3, 6, 9]])
想要区分时,另一个选择是使用np.newaxis:
>>> a = np.array([1, 2, 3])
>>> a
array([1, 2, 3])
>>> a[:, np.newaxis]
array([[1],
[2],
[3]])
>>> a[np.newaxis, :]
array([[1, 2, 3]])