How to replace a random value from an array with another one

Question

So I have this array:

TEST = np.array([[1,2,3,4,5], [0,0,1,1,1], [0,1,2,4,5]])

And I want to replace a single random number from the array with 6.

With an exact value I would replace him with:

TEST[0,0] = 6

But since it’s a random number that alternates I cannot do that (or maybe I can and just don’t know how)

We also have repeated values, so I cannot just pick a value 0 and replace it for 6 since it would replace all the zeros (I think).

So does anyone know how to replace a random number in this specific array? (as an example).

Asked By: UserNameM

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Source

Answer 1

I think you’re saying you want to do this;

import numpy as np
import random

test = np.array([[1,2,3,4,5], [0,0,1,1,1], [0,1,2,4,5]])

n1 = random.randrange(test.shape[0])
n2 = random.randrange(test.shape[1])

test[n1][n2] = 6

Answered By: CryptoFool

Answer 2

For a slightly different take, numpy.put() allows you to replace and value at the flattened index in an array.

So in the case of:

test = np.array([[1,2,3,4,5], [0,0,1,1,1], [0,1,2,4,5]])

you could pick a number in the range 0 – 15 and put() your value there.

test = np.array([[1,2,3,4,5], [0,0,1,1,1], [0,1,2,4,5]])
i = np.random.randint(np.prod(test.shape))
test.put(i, 100)

Turning test into something like (if i turned out to be 11):

array([[  1,   2,   3,   4,   5],
       [  0,   0,   1,   1,   1],
       [  0, 100,   2,   4,   5]])

Answered By: Mark

How to replace a random value from an array with another one

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