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).

Ops, it's supposed to be "TEST[0:1,0:1] = 6" I will change it, thank you! — UserNameM
– UserNameM, Commented Oct 23, 2022 at 0:58
Just like TEST[0,0] = 6 would replace the value at [0,0], you can pick the row and column indices of the cell to replace and use them as an index into your structure. E.g., TEST[x,y] = 6, with x and y sampled to pick the cell you want to update. — joanis
– joanis, Commented Oct 23, 2022 at 0:58
Why slices instead of just indexes? Is that what you're asking? I'm not sure I understand the question. BTW, welcome to Stack Overflow! Check out the tour, and How to Ask if you want tips. — wjandrea
– wjandrea, Commented Oct 23, 2022 at 0:58

Mark · Accepted Answer · 2022-10-23 01:18:06Z

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 Oct 23, 2022 at 1:18

Mark

92.7k8 gold badges116 silver badges156 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

CryptoFool · Accepted Answer · 2022-10-23 01:07:09Z

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

edited Oct 23, 2022 at 1:07

answered Oct 23, 2022 at 1:03

CryptoFool

23.4k5 gold badges31 silver badges55 bronze badges

1 Comment

UserNameM Over a year ago

Yes! It was as simple as that but I wasn't thinking very clear. Thank you very much!

Collectives™ on Stack Overflow

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

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related