numpy arrays

[Steven D'Aprano]

On Wed, 23 Mar 2016 09:06 pm, Heli wrote:

> Hi,
> 
> I have a 2D numpy array like this:
> 
> [[1,2,3,4],
>  [1,2,3,4],
>  [1,2,3,4]
>  [1,2,3,4]]
> 
> Is there any fast way to convert this array to
> 
> [[1,1,1,1],
>  [2,2,2,2]
>  [3,3,3,3]
>  [4,4,4,4]]



Mathematically, this is called the "transpose" of the array, and you can do
that in numpy:

py> import numpy as np
py> arr = np.array(
... [[1,2,3,4],
...  [1,2,3,4],
...  [1,2,3,4],
...  [1,2,3,4]])
py> arr
array([[1, 2, 3, 4],
       [1, 2, 3, 4],
       [1, 2, 3, 4],
       [1, 2, 3, 4]])
py> arr.T
array([[1, 1, 1, 1],
       [2, 2, 2, 2],
       [3, 3, 3, 3],
       [4, 4, 4, 4]])



-- 
Steven