Struct Gamma 

pub struct Gamma { /* private fields */ }

Gamma distribution (shape/rate parameterization), conjugate prior for Poisson likelihood.

After observing a count c (one observation), the posterior is Gamma(shape + c, rate + 1).

Implementations

impl Gamma

pub fn new(shape: f64, rate: f64) -> Result<Self>

Create a Gamma distribution with given shape (α) and rate (β).

Both must be positive.

pub fn shape(&self) -> f64

Shape parameter (α).

pub fn rate(&self) -> f64

Rate parameter (β).

pub fn update_poisson(&self, count: u64) -> Self

Posterior after observing a single Poisson count.

pub fn update_poisson_batch(&self, counts: &[u64]) -> Self

Posterior after observing multiple Poisson counts.

Trait Implementations

impl Clone for Gamma

fn clone(&self) -> Gamma

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Gamma

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

Formats the value using the given formatter.

impl Distribution for Gamma

fn pdf(&self, x: f64) -> f64

Probability density (or mass) function at x.

fn cdf(&self, x: f64) -> f64

Cumulative distribution function at x.

fn mean(&self) -> f64

Distribution mean.

fn variance(&self) -> f64

Distribution variance.

fn std_dev(&self) -> f64

Distribution standard deviation (default: sqrt of variance).

impl Copy for Gamma