Sampling from a list of integers without repetition

New to Julia
1

Given a vector of integers

a = collect(1:10)

I would like to randomly sample 5 integers with guaranteed non-repetition. As far as I know,

b = rand(a, 10)

does not guarantee that. This is easily demonstrated via

for i in 1:100
    println(rand(1:10, 8))
end

How can it be done? Thanks.

I found the answer on Slack: Julia : generating unique random integer array - Stack Overflow

StatsBase.rand(using StatsBase
a = sample(1:100, 10, replace = false)

Given that rand has 173 functions in its dispatch table, that adding a replace argument` in several of them could prove very useful.

5 Likes
2

sample is the correct method (and terminology) here. rand is for random number generation, and if it guaranteed unique values then the sequence would no longer be random.

8 Likes
3

To add to @tbeason’s excellent answer: the technical term for this is sampling without replacement, while rand is IID (as approximated by a pseudorandom process).

Because of this, adding such an option to rand would not be the right place for this functionality. If you know the term, sample is also more discoverable.

1 Like
4

tpThank you all!