python: How do I expand a numpy array with adjacent duplicate columns?

Question

What I am trying to achieve is that I have a matrix like that:

axy
axy
axy
axy

And I want to expand that matrix so that it will become:

aaaxxxyyy
aaaxxxyyy
aaaxxxyyy
aaaxxxyyy

Is there a function that I can use to manage this transformation easily? I would like to use a better way than tiling each column separately and appending them back.

Thanks in advance.

Just for some matrix operations with another one, I don't further need that expanded version. — Mahir Kerim Serbetcioglu
– Mahir Kerim Serbetcioglu, Commented Aug 6, 2015 at 6:42

Imanol Luengo · Accepted Answer · 2015-08-05 15:22:58Z

7

You can use np.repeat:

>>> import numpy as np
>>> a = np.arange(9).reshape(3,3)
>>> a
array([[0, 1, 2],
       [3, 4, 5],
       [6, 7, 8]])
>>> b = np.repeat(a, 3, axis=1) # array, times, axis
>>> b
array([[0, 0, 0, 1, 1, 1, 2, 2, 2],
       [3, 3, 3, 4, 4, 4, 5, 5, 5],
       [6, 6, 6, 7, 7, 7, 8, 8, 8]])

answered Aug 5, 2015 at 15:22

Imanol Luengo

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