how to randomly sample in 2D matrix in numpy

Question

I have a 2d array/matrix like this, how would I randomly pick the value from this 2D matrix, for example getting value like [-62, 29.23]. I looked at the nump

Answer 1

Just use a random index (in your case 2 because you have 3 dimensions):

import numpy as np

Space_Position = np.array(Space_Position)

random_index1 = np.random.randint(0, Space_Position.shape[0])
random_index2 = np.random.randint(0, Space_Position.shape[1])

Space_Position[random_index1, random_index2]  # get the random element.

---

The alternative is to actually make it 2D:

Space_Position = np.array(Space_Position).reshape(-1, 2)

and then use one random index:

Space_Position = np.array(Space_Position).reshape(-1, 2)      # make it 2D
random_index = np.random.randint(0, Space_Position.shape[0])  # generate a random index
Space_Position[random_index]                                  # get the random element.

If you want N samples with replacement:

N = 5

Space_Position = np.array(Space_Position).reshape(-1, 2)                # make it 2D
random_indices = np.random.randint(0, Space_Position.shape[0], size=N)  # generate N random indices
Space_Position[random_indices]  # get N samples with replacement

or without replacement:

Space_Position = np.array(Space_Position).reshape(-1, 2)  # make it 2D
random_indices = np.arange(0, Space_Position.shape[0])    # array of all indices
np.random.shuffle(random_indices)                         # shuffle the array
Space_Position[random_indices[:N]]  # get N samples without replacement

Answer 2

Space_Position[np.random.randint(0, len(Space_Position))]
[np.random.randint(0, len(Space_Position))]

gives you what you want