Function sample_weighted

pub fn sample_weighted<R, F, X>(
    rng: &mut R,
    length: usize,
    weight: F,
    amount: usize,
) -> Result<IndexVec, WeightError>
where
    R: Rng + ?Sized,
    F: Fn(usize) -> X,
    X: Into<f64>,

Randomly sample exactly amount distinct indices from 0..length

Results are in arbitrary order (there is no guarantee of shuffling or ordering).

Function weight is called once for each index to provide weights.

This method is used internally by the slice sampling methods, but it can sometimes be useful to have the indices themselves so this is provided as an alternative.

Error cases:

• WeightError::InvalidWeight when a weight is not-a-number or negative.
• WeightError::InsufficientNonZero when fewer than amount weights are positive.

This implementation uses O(length + amount) space and O(length) time.