Stack a list of numpy arrays

Question

I have a list of numpy arrays that are of the following shapes:

(16, 250, 2)
(7, 250, 2)
(1, 250, 2)

I'm trying to stack them all together so they are a single numpy array of shape :

(24, 250, 2)

I tried using np.stack but I get the error:

ValueError: all input arrays must have the same shape

Try concatenate with axis=0.

hpaulj
– hpaulj

2020-05-28 06:47:47 +00:00
Commented May 28, 2020 at 6:47 — hpaulj
– hpaulj, Commented May 28, 2020 at 6:47
perfect, thank you very much.

CentauriAurelius
– CentauriAurelius

2020-05-28 06:49:08 +00:00
Commented May 28, 2020 at 6:49 — CentauriAurelius
– CentauriAurelius, Commented May 28, 2020 at 6:49

Dhaval Taunk · Accepted Answer · 2020-05-28 06:49:41Z

2

You can use np.concatenate: You will get this:-

a = np.random.rand(16,250,2)
b = np.random.rand(7,250,2)
c = np.random.rand(1,250,2)
print(np.shape(np.concatenate([a,b,c], axis=0))

Output:

(24,250,2)

answered May 28, 2020 at 6:49

Dhaval Taunk

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Comments

Aly Hosny · Accepted Answer · 2020-05-28 06:50:13Z

1

The trick is to use the right stacking method, in your case since you are stacking vertically you should use np.vstack

import numpy as np

a = np.random.random((16, 250, 2))
b = np.random.random((7, 250, 2))
c = np.random.random((1, 250, 2))

arr = np.vstack((a,b,c))
arr.shape
(24, 250, 2)

answered May 28, 2020 at 6:50

Aly Hosny

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1 Comment

CentauriAurelius Over a year ago

this also works for my list, if i do arr = np.vstack(mylist)

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