CODEWITHSUNDEEP
arraysbashrandom
charlesD
charlesD

Reputation: 37

How can I randomly weight an element from an array and then pick it based on those weights?

I want to pseudo-randomly pick one element from an array of 5 elements: I want to control the occurrence probability of each of those 5 elements.

Example: I have an array like this: [A B C D E]

I have seen that I can weight a random selection from an array here: Weighted random selection from array.

How can I weight elements contained in an array like this?

Upvotes: 1

Views: 544

Answers (1)

glenn jackman
glenn jackman

Reputation: 247210

You'd use the bash builtin variable RANDOM, with a little arithmetic

weighted_selection() {
    local ary=("$@")
    case $(( RANDOM % 10 )) in
        0) index=0 ;;      # one out of ten
        1) index=1 ;;      # one out of ten
        2|3) index=2 ;;    # two out of ten
        4|5) index=3 ;;    # two out of ten
        *) index=4 ;;      # remaining is four out of ten
    esac
    echo ${ary[index]}
}

Let's test it:

a=(A B C D E)
declare -A count
for ((i=1; i<1000; i++)); do
    (( count[$(weighted_selection "${a[@]}")]++ ))
done
declare -p count

outputs

declare -A count='([A]="99" [B]="100" [C]="211" [D]="208" [E]="381" )'

Upvotes: 2

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