what's the difference between (4,) and (4,1) for the shape in Numpy?

Question

I have two ndarray A and B, one has the shape (4,) and another (4,1).

When I want to calculate the cosine distance using this, it throws some exceptions that complains the two objects are not aligned

Does anyone have ideas about this? Thanks!

Answer 1

One is a 1-dimensional array, the other is a 2-dimensional array.

Example:

>>> import numpy as np
>>> a = np.arange(4).reshape(4,1)
>>> a
array([[0],
       [1],
       [2],
       [3]])
>>> a.ravel()
array([0, 1, 2, 3])
>>> a.squeeze()
array([0, 1, 2, 3])
>>> a[:,0]
array([0, 1, 2, 3])
>>>
>>> a[:,0].shape
(4,)