Struct Binomial

pub struct Binomial { /* private fields */ }

The binomial distribution Binomial(n, p).

The binomial distribution is a discrete probability distribution which describes the probability of seeing k successes in n independent trials, each of which has success probability p.

Density function

f(k) = n!/(k! (n-k)!) p^k (1-p)^(n-k) for k >= 0.

Plot

The following plot of the binomial distribution illustrates the probability of k successes out of n = 10 trials with p = 0.2 and p = 0.6 for 0 <= k <= n.

Example

use rand_distr::{Binomial, Distribution};

let bin = Binomial::new(20, 0.3).unwrap();
let v = bin.sample(&mut rand::rng());
println!("{} is from a binomial distribution", v);

Numerics

The implementation uses f64 internally, which leads to rounding errors for big numbers. For very large samples (> 2^53) the least significant bits of the output will not be random. This means that something like bin.sample(&mut rand::rng()) % 4 will not follow the correct distribution. The more significant bits should be correctly distributed.

Implementations

impl Binomial

pub fn new(n: u64, p: f64) -> Result<Binomial, Error>

Construct a new Binomial with the given shape parameters n (number of trials) and p (probability of success).

Trait Implementations

impl Clone for Binomial

fn clone(&self) -> Binomial

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Binomial

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Distribution<u64> for Binomial

fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u64

Generate a random value of T, using rng as the source of randomness.

fn sample_iter<R>(self, rng: R) -> Iter<Self, R, T>

where R: Rng, Self: Sized,

Create an iterator that generates random values of T, using rng as the source of randomness.

fn map<F, S>(self, func: F) -> Map<Self, F, T, S>

where F: Fn(T) -> S, Self: Sized,

Map sampled values to type S

impl PartialEq for Binomial

fn eq(&self, other: &Binomial) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Binomial

impl StructuralPartialEq for Binomial