Struct std::rand::distributions::gamma::Gamma
[−]
[src]
pub struct Gamma { repr: GammaRepr, }
rand
): use rand
from crates.io
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
.
[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
Fields
repr | Unstable ( rand ): use |
Methods
impl Gamma
fn new(shape: f64, scale: f64) -> Gamma
rand
): use rand
from crates.io
Construct an object representing the Gamma(shape, scale)
distribution.
Panics if shape <= 0
or scale <= 0
.