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Asked: 2026-06-11T06:17:54+00:00

I’m trying to sample from a multinomial in order to pull out elements of

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I’m trying to sample from a multinomial in order to pull out elements of a vector by their weight.

For example, given the vector v <- c(10, 30, 60) I would like something like:
[ 3, 3, 2, 3, 1, 2, 3, 2, 3, 3 ]

Here’s the best I can come up with so far:

v <- c(10, 30, 60)
apply(rmultinom(10,1,v),2,function(x) which(x==1))

This works fine for small N and K, but I actually need to generate 100k samples from an index set from 1 to 100k, since this method requires a NxK temporary matrix it is obviously not going to work. I could just use a for loop as well, but I was hoping there is existing methods to do this.

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1 Answer

  1. Editorial Team

    You can just use sample with the prob parameter

    sample(length(v), 10, replace = T, prob = v)

    Some sample output:

    v <- c(10, 30, 60)
out <- sample(length(v), 100, replace = T, prob = v)
out
#  [1] 3 3 3 3 3 3 3 2 2 2 2 3 3 1 3 3 3 3 2 2 3 2 1 3 3 2 3 3 3 2 2 3 2 3 1 2 2 3 3
# [40] 3 2 2 2 2 3 2 1 3 3 3 3 3 3 3 3 1 2 2 3 3 3 2 3 3 3 1 3 3 3 2 1 3 3 3 2 2 3 3
# [79] 3 3 1 3 2 3 3 3 3 2 3 3 2 2 3 2 3 2 2 2 2 3
table(out)
#out
# 1  2  3 
# 8 33 59
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