# 1. Introduction

    library(bage)
    library(rvec)
    #>
    #> Attaching package: 'rvec'
    #> The following objects are masked from 'package:stats':
    #>
    #>     sd, var
    #> The following object is masked from 'package:base':
    #>
    #>     rank
    library(dplyr)
    #>
    #> Attaching package: 'dplyr'
    #> The following objects are masked from 'package:stats':
    #>
    #>     filter, lag
    #> The following objects are masked from 'package:base':
    #>
    #>     intersect, setdiff, setequal, union
    library(ggplot2)

    mod <- mod_pois(injuries ~ age : sex + age : ethnicity + year,
                    data = injuries,
                    exposure = popn) |>
      set_prior(year ~ AR1())
    mod
    #> -- Unfitted Poisson model --
    #>
    #>      injuries ~ age:sex + age:ethnicity + year
    #>
    #>   (Intercept) ~ NFix()
    #>          year ~ AR1()
    #>       age:sex ~ RW()
    #> age:ethnicity ~ RW()
    #>
    #>      dispersion: mean=1
    #>        exposure: popn
    #>         var_age: age
    #>   var_sexgender: sex
    #>        var_time: year
    #>          n_draw: 1000