gam_problem/
dispersion.rs

1//! Dispersion/scale contract used by covariance and reference-distribution code.
2
3use serde::{Deserialize, Serialize};
4
5/// Dispersion contract used by inferential covariance and reference distributions.
6///
7/// `Known(phi)` is used for fixed-scale exponential-family fits such as
8/// Poisson and Binomial (`phi = 1`). `Estimated(phi)` is used when the
9/// residual/likelihood scale is estimated from the data, e.g. Gaussian
10/// (`phi = sigma^2`) and Gamma (`phi = 1 / shape`). Stored covariance
11/// matrices are scaled by this `phi`.
12#[derive(Clone, Copy, Debug, PartialEq, Serialize, Deserialize)]
13pub enum Dispersion {
14    Known(f64),
15    Estimated(f64),
16}
17
18impl Dispersion {
19    #[inline]
20    pub const fn phi(self) -> f64 {
21        match self {
22            Self::Known(phi) | Self::Estimated(phi) => phi,
23        }
24    }
25
26    #[inline]
27    pub const fn is_estimated(self) -> bool {
28        matches!(self, Self::Estimated(_))
29    }
30}
31
32impl Default for Dispersion {
33    fn default() -> Self {
34        Self::Known(1.0)
35    }
36}
gam_problem/dispersion.rs

gam_problem/
dispersion.rs
