Create Dispersion Structure Specification

This function creates a dispersion structure object that specifies priors for the overdispersion parameter of the negative binomial likelihood for the case timeseries. phi controls how much the observed counts vary around the expected trend beyond Poisson noise: smaller values allow more overdispersion (noisier counts relative to the mean), larger values approach Poisson-like variance.

Usage

dispersion_structure(phi_mean = NULL, phi_sd = NULL)

Arguments

phi_mean

Numeric scalar specifying the prior mean for the negative binomial dispersion parameter. Must be positive. Optional - if not provided, no priors will be set.

phi_sd

Numeric scalar specifying the prior standard deviation for the dispersion parameter. Must be positive. Optional - if not provided, no priors will be set.

Value

An object of class EpiStrainDynamics.dispersion containing:

mean

The prior mean for phi

sd

The prior standard deviation for phi

priors_provided

Integer flag passed to the Stan model: 1 if no priors were supplied (Stan's built-in default prior is used), 2 if priors were supplied (the phi_mean/phi_sd values are used as the prior)

Examples

# Create dispersion structure
disp_struct <- dispersion_structure(phi_mean = 2.0, phi_sd = 0.5)