Avoid duplicate random values

Question

Following this post, I can generate random integers with a fixed sum. However, I want to avoid any duplicate numbers (such as 20 in the following example):

import numpy as np

_sum = 100
n = 5
rnd_array = np.random.multinomial(_sum, np.ones(n)/n, size=1)[0]
rnd_array

>>> array([20, 24, 20, 21, 15])

How could I achieve this?

The answer is in this link. This question has been answered I guess stackoverflow.com/questions/22842289/… — Althaf1467
– Althaf1467, Commented Jan 22, 2019 at 11:42
@Althaf1467 - In terms of generating random numbers then yes, the post you linked to solves that. But I also want the random values to sum up to a specific value at the same time. — Joseph
– Joseph, Commented Jan 22, 2019 at 12:19

Charles Landau · Accepted Answer · 2019-01-22 12:36:33Z

4

random.sample returns a list of unique values (see the docs.) It's called like this:

sample = random.sample(range(100), 5)

Edit: For using this to get fixed sum, I suggest reading this thread where the important code is:

from random import*
def f(n,s):
  r=min(s,1)
  x=uniform(max(0,r-(r-s/n)*2),r)
  return n<2and[s]or sample([x]+f(n-1,s-x),n)

edited Jan 22, 2019 at 12:36

answered Jan 22, 2019 at 11:39

Charles Landau

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3 Comments

Joseph Over a year ago

Your answer solves half the the problem :). The random values generated need to sum to a specific value (in my example, 5 random integers should sum to 100).

Charles Landau Over a year ago

@Joseph I made an edit to show how sample is used in that context

Joseph Over a year ago

Thanks for the edit. The float values generated are indeed random and sum to 100. To get it to integer values which I needed, I used x = int(uniform(max(0, r - (r - s/n) * 2), r)). Thank you again :)

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