How to merge 2 numpy arrays?

Question

I feel like there is some documentation I am missing, but I can't find anything on this specific example - everything is just about concatenating or stacking arrays.

I have array x and array y both of shape (2,3)

x = [[1,2,3],[4,5,6]]

y = [[7,8,9],[10,11,12]]

I want array z with shape (2,3,2) that looks like this

z = [[[1,7],[2,8],[3,9]],[[4,10],[5,11],[6,12]]]

z = [1,7] [2,8] [3,9]
    [4 10] [5 11] [6 12]

basically joins the x and y element at each position.

If you can look at the Python code for stack and dstack. They expand the array dimensions and concatenate on one axis. stack is new function in this family. — hpaulj
– hpaulj, Commented May 22, 2016 at 3:05

user20160 · Accepted Answer · 2016-05-22 02:29:48Z

4

Sounds like the function you're looking for is stack(), using it to stack along the 3rd dimension.

import numpy as np

x = np.asarray([[1,2,3],[4,5,6]])
y = np.asarray([[7,8,9],[10,11,12]])
z = np.stack((x, y), 2)

answered May 22, 2016 at 2:29

user20160

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Darius · Accepted Answer · 2016-05-22 02:34:47Z

3

If you have two-dimensional matrices, you can use numpy.dstack():

z = np.dstack((x, y))

answered May 22, 2016 at 2:34

Darius

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John1024 · Accepted Answer · 2016-05-22 02:30:44Z

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In [39]: z = np.concatenate((x[...,None], y[...,None]), axis=2)

In [40]: z
Out[40]: 
array([[[ 1,  7],
        [ 2,  8],
        [ 3,  9]],

       [[ 4, 10],
        [ 5, 11],
        [ 6, 12]]])

answered May 22, 2016 at 2:30

John1024

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