rand::distributions::gamma::Gamma - Rust
Description: API documentation for the Rust `Gamma` struct in crate `rand`.
Keywords: rust, rustlang, rust-lang, Gamma

# Struct rand::distributions::gamma::Gamma [−] [src]

    pub struct Gamma { /* fields omitted */ }

The Gamma distribution `Gamma(shape, scale)` distribution.

The density function of this distribution is

    f(x) =  x^(k - 1) * exp(-x / θ) / (Γ(k) * θ^k)

where `Γ` is the Gamma function, `k` is the shape and `θ` is the scale and both `k` and `θ` are strictly positive.

The algorithm used is that described by Marsaglia & Tsang 2000[1], falling back to directly sampling from an Exponential for `shape == 1`, and using the boosting technique described in [1] for `shape < 1`.

# Example

    use rand::distributions::{IndependentSample, Gamma};

    let gamma = Gamma::new(2.0, 5.0);
    let v = gamma.ind_sample(&mut rand::thread_rng());
    println!("{} is from a Gamma(2, 5) distribution", v);

[1]: George Marsaglia and Wai Wan Tsang. 2000. "A Simple Method for Generating Gamma Variables" ACM Trans. Math. Softw. 26, 3 (September 2000), 363-372. DOI:10.1145/358407.358414

## Methods

### `impl Gamma`
[src]

#### `fn new(shape: f64, scale: f64) -> Gamma`
[src]

Construct an object representing the `Gamma(shape, scale)` distribution.

Panics if `shape <= 0` or `scale <= 0`.

## Trait Implementations

### `impl Clone for Gamma`
[src]

#### `fn clone(&self) -> Gamma`
[src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)`
1.0.0
[src]

Performs copy-assignment from `source`. Read more

### `impl Copy for Gamma`
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### `impl Debug for Gamma`
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#### `fn fmt(&self, __arg_0: &mut Formatter) -> Result`
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Formats the value using the given formatter.

### `impl Sample<f64> for Gamma`
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#### `fn sample<R: Rng>(&mut self, rng: &mut R) -> f64`
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Generate a random value of `Support`, using `rng` as the source of randomness. Read more

### `impl IndependentSample<f64> for Gamma`
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#### `fn ind_sample<R: Rng>(&self, rng: &mut R) -> f64`
[src]

Generate a random value.

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