Repeat Array while Maintaining Order within group

January 4, 2022

I have the below array and would like to repeat each array n times.

x_array

[array([14.91488012,  1.2986064 ,  4.98965322]),
 array([2.39389187e+02, 1.04442059e-01, 3.06391338e-01]),
 array([ 48.19437348, 201.09951372,   0.35223001]),
 array([ 19.96978171, 367.52578786,   0.68676553]),
 array([0.55120466, 0.27133609, 0.75646697]),
 array([8.21287360e+02, 1.76495077e+02, 4.87263691e-01]),
 array([184.03439377,   1.24823107,   5.33109884]),
 array([575.59800297, 186.4650814 ,   2.21028258]),
 array([0.50308552, 3.09976082, 0.10537899]),
 array([1.02259912e+00, 1.52282513e+02, 1.15085308e-01])]

I’ve tried np.repeat(x_array, 2) but this doesn’t preserve the order of the matrix/array. I’ve also tried x_array*2, but this seems to just put the new array at the bottom. I was hopping to repeat x_array[0] n times and do the same for the next set of arrays, so that I have n total of each in order.

Thanks in advance.

>Solution :

You just need to specify the axis:

>>> np.repeat(x_array, 2, axis=0)
array([[1.49149e+01, 1.29861e+00, 4.98965e+00],
       [1.49149e+01, 1.29861e+00, 4.98965e+00],
       [2.39389e+02, 1.04442e-01, 3.06391e-01],
       [2.39389e+02, 1.04442e-01, 3.06391e-01],
       ...,
       [5.03086e-01, 3.09976e+00, 1.05379e-01],
       [5.03086e-01, 3.09976e+00, 1.05379e-01],
       [1.02260e+00, 1.52283e+02, 1.15085e-01],
       [1.02260e+00, 1.52283e+02, 1.15085e-01]])

From the docs:

numpy.repeat(a, repeats, axis=None)

…

axis int, optional
The axis along which to repeat values. By default, use the flattened input array, and return a flat output array.

(added bold)