How do I select a random item from a weighted array in Julia?
Use the StatsBase.jl package, i.e.
Pkg.add("StatsBase") # Only do this once, obviouslyusing StatsBaseitems = ["a", 2, 5, "h", "hello", 3]weights = [0.1, 0.1, 0.2, 0.2, 0.1, 0.3]sample(items, Weights(weights))Or if you want to sample many:
# With replacementmy_samps = sample(items, Weights(weights), 10)# Without replacementmy_samps = sample(items, Weights(weights), 2, replace=false)(In Julia < 1.0, Weights was called WeightVec).
You can learn more about Weights and why it exists in the docs. The sampling algorithms in StatsBase are very efficient and designed to use different approaches depending on the size of the input.
Here's a much simpler approach which only uses Julia's base library:
sample(items, weights) = items[findfirst(cumsum(weights) .> rand())]Example:
>>> sample(["a", 2, 5, "h", "hello", 3], [0.1, 0.1, 0.2, 0.2, 0.1, 0.3])"h"This is less efficient than StatsBase.jl, but for small vectors it's fine.
Also, if weights is not a normalized vector, you need to do: cumsum(weights ./ sum(weights)).