1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
use crate::{ChiSquaredParams, DistributionError, SampleableDistribution};
use crate::{DependentJoint, Distribution, IndependentJoint, RandomVariable};
use rand::prelude::*;
use rand_distr::ChiSquared as RandChiSquared;
use std::{ops::BitAnd, ops::Mul};
#[derive(Clone, Debug)]
pub struct ChiSquared;
#[derive(thiserror::Error, Debug)]
pub enum ChiSquaredError {
#[error("'k' must be positibe")]
KMustBePositive,
}
impl Distribution for ChiSquared {
type Value = f64;
type Condition = ChiSquaredParams;
fn p_kernel(&self, x: &Self::Value, theta: &Self::Condition) -> Result<f64, DistributionError> {
let k = theta.k();
Ok(x.powf(k / 2.0 - 1.0) * (-x / 2.0).exp())
}
}
impl<Rhs, TRhs> Mul<Rhs> for ChiSquared
where
Rhs: Distribution<Value = TRhs, Condition = ChiSquaredParams>,
TRhs: RandomVariable,
{
type Output = IndependentJoint<Self, Rhs, f64, TRhs, ChiSquaredParams>;
fn mul(self, rhs: Rhs) -> Self::Output {
IndependentJoint::new(self, rhs)
}
}
impl<Rhs, URhs> BitAnd<Rhs> for ChiSquared
where
Rhs: Distribution<Value = ChiSquaredParams, Condition = URhs>,
URhs: RandomVariable,
{
type Output = DependentJoint<Self, Rhs, f64, ChiSquaredParams, URhs>;
fn bitand(self, rhs: Rhs) -> Self::Output {
DependentJoint::new(self, rhs)
}
}
impl SampleableDistribution for ChiSquared {
fn sample(
&self,
theta: &Self::Condition,
rng: &mut dyn RngCore,
) -> Result<Self::Value, DistributionError> {
let k = theta.k();
let chi_squared = match RandChiSquared::new(k) {
Ok(v) => Ok(v),
Err(e) => Err(DistributionError::Others(e.into())),
}?;
Ok(rng.sample(chi_squared))
}
}
#[cfg(test)]
mod tests {
#[test]
fn it_works() {
assert_eq!(2 + 2, 4);
}
}