(Python Numpy) How can I create new 3D array from given 2D array?

Question

I want to do something like this:

I give a 2D numpy array:

[[ 1, 2, 3],
 [ 4, 5, 6],
 [ 7, 8, 9]]

And I want to get a 3D numpy array:

[[[1, 1, 1],
  [2, 2, 2],
  [3, 3, 3]],

 [[4, 4, 4],
  [5, 5, 5],
  [6, 6, 6]],

 [[7, 7, 7],
  [8, 8, 8],
  [9, 9, 9]]]

Does numpy has a function that can do this transformation?

jkr · Accepted Answer · 2021-04-11 15:00:02Z

3

One can use np.tile. Before doing this, a dimension needs to be added at the end of the array.

In [28]: x = np.array([[ 1, 2, 3],
    ...:  [ 4, 5, 6],
    ...:  [ 7, 8, 9]])

In [29]: np.tile(x[..., None], 3)
Out[29]: 
array([[[1, 1, 1],
        [2, 2, 2],
        [3, 3, 3]],

       [[4, 4, 4],
        [5, 5, 5],
        [6, 6, 6]],

       [[7, 7, 7],
        [8, 8, 8],
        [9, 9, 9]]])

answered Apr 11, 2021 at 15:00

jkr

19.6k5 gold badges48 silver badges78 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Amit Vikram Singh · Accepted Answer · 2021-04-11 14:59:43Z

2

First extend the dimension of 2D array using arr[:, :, np.newaxis], this changes dimension from (3, 3) to (3, 3, 1). Now repeat this 3D array along the third dimension.

Use:

arr = np.repeat(arr[:, :, np.newaxis], 3, -1)

Output:

>>> np.repeat(arr[:, :, np.newaxis], 3, -1)
array([[[1, 1, 1],
        [2, 2, 2],
        [3, 3, 3]],

       [[4, 4, 4],
        [5, 5, 5],
        [6, 6, 6]],

       [[7, 7, 7],
        [8, 8, 8],
        [9, 9, 9]]])

answered Apr 11, 2021 at 14:59

Amit Vikram Singh

2,12812 silver badges22 bronze badges

Collectives™ on Stack Overflow

(Python Numpy) How can I create new 3D array from given 2D array?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related