Make a NxN array of 1x3 arrays of random numbers (python)

Question

Is there a way to make a NxN array (so 2d array) of elements, where each element is an array of 3 numbers randomly chosen between 0 and 1?

Output should look something like this:

(0.2,0.45,0.98), (0.7,0.58,0.11) ...
(1.0,0.05,0.63, ...
.
.
.

etc.

I've been trying to do this but there must be a more elegant way. Code included below:

import numpy as  np
import matplotlib.pyplot as plt

lat = []

for _ in range(2):

        w = []

        for _ in range(2):
                a = np.random.uniform(0.0,1.0)
                b = np.random.uniform(0.0,1.0)
                c = np.random.uniform(0.0,1.0)

                D = np.array([a,b,c])

                w.append(D)

        lat.append(w)

        if _ >= 1:
                np.hstack(lat)

Cory Kramer · Accepted Answer · 2017-10-20 13:19:52Z

1

You can use numpy.random.rand where the first argument is the number of rows you want to generate, then the second argument can be 3 in your case for each row.

>>> import numpy as np
>>> np.random.rand(10,3)
array([[ 0.80325895,  0.70250496,  0.4256057 ],
       [ 0.28863352,  0.14066084,  0.08918333],
       [ 0.52669678,  0.07641594,  0.92869148],
       [ 0.40105226,  0.88909989,  0.25459293],
       [ 0.8202674 ,  0.34435551,  0.49131868],
       [ 0.14251546,  0.51029693,  0.54037975],
       [ 0.07118544,  0.95467079,  0.87722367],
       [ 0.33530285,  0.64395738,  0.8289817 ],
       [ 0.5461907 ,  0.93165573,  0.73256816],
       [ 0.31204938,  0.38230589,  0.49739997]])

answered Oct 20, 2017 at 13:19

Cory Kramer

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1 Comment

user8188120 Over a year ago

So if i use: np.random.rand(3,3,3) That gives me the matrix I described in the question but with the three elements going into the 3rd dimension so it's like a data cube. Thank you CoryKramer!

Yulian · Accepted Answer · 2017-10-20 13:39:37Z

You can use numpy.reshape to reshape randomly generated numbers.

>>> N = 3
>>> np.random.rand(N*N*3).reshape([N,N,3])
array([[[ 0.48513983,  0.49582462,  0.96211702],
        [ 0.95061997,  0.63674441,  0.51228963],
        [ 0.06988701,  0.9018317 ,  0.63418989]],

       [[ 0.31213247,  0.75325276,  0.04600117],
        [ 0.23449785,  0.04731562,  0.89007085],
        [ 0.25746369,  0.96337201,  0.6032985 ]],

       [[ 0.2207508 ,  0.43560328,  0.75067189],
        [ 0.84054857,  0.28190793,  0.08875157],
        [ 0.00419059,  0.13464854,  0.63074635]]])

Result is a 2d array of array of 3 numbers.

>>> temp = np.random.rand(N*N*3).reshape([N,N,3])
>>> temp[0][0]
array([ 0.48513983,  0.49582462,  0.96211702])

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