Struct BetaPosterior 

pub struct BetaPosterior {
    pub alpha: f64,
    pub beta: f64,
    pub alpha0: f64,
    pub beta0: f64,
}

Beta distribution posterior for a probability parameter (Beta-Bernoulli).

Models θ ∈ [0, 1] with a Beta(α, β) prior; observing a success increments α, a failure increments β. The original prior (α₀, β₀) is retained so that observations can report the true trial count for any prior, not just the uniform one.

Fields

alpha: f64

Alpha parameter (prior pseudo-successes + observed successes)

beta: f64

Beta parameter (prior pseudo-failures + observed failures)

alpha0: f64

Prior alpha (α₀) — retained for correct observation counting.

beta0: f64

Prior beta (β₀) — retained for correct observation counting.

Implementations

impl BetaPosterior

pub fn uniform() -> Self

Create with uniform prior (α = β = 1)

pub fn jeffreys() -> Self

Create with Jeffreys prior (α = β = 0.5)

pub fn new(alpha: f64, beta: f64) -> Self

Create with a custom prior Beta(alpha, beta).

pub fn observe_success(&mut self)

Update posterior with a success observation

pub fn observe_failure(&mut self)

Update posterior with a failure observation

pub fn observe(&mut self, success: bool)

Update based on boolean outcome

pub fn mean(&self) -> f64

Posterior mean

pub fn mode(&self) -> Option<f64>

Posterior mode (for α, β > 1)

pub fn variance(&self) -> f64

Posterior variance

pub fn std_dev(&self) -> f64

Posterior standard deviation

pub fn sample<R: Rng>(&self, rng: &mut R) -> f64

Sample from the posterior

pub fn credible_interval(&self, probability: f64) -> (f64, f64)

95% credible interval (approximate using normal approximation for large counts)

pub fn observations(&self) -> f64

Number of observed Bernoulli trials, (α − α₀) + (β − β₀).

This subtracts the stored prior pseudo-counts, so it is correct for any prior — uniform Beta(1, 1), Jeffreys Beta(0.5, 0.5), or informative.

pub fn decay(&mut self, factor: f64)

Apply decay to move toward the stored prior (for non-stationary environments)

Trait Implementations

impl Clone for BetaPosterior

fn clone(&self) -> BetaPosterior

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for BetaPosterior

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

Formats the value using the given formatter.

impl Default for BetaPosterior

fn default() -> Self

Returns the “default value” for a type.