Defines a list specifying the structure of the observation
model. Custom settings can be supplied which override the defaults.

```
obs_opts(
family = "negbin",
phi = c(0, 1),
weight = 1,
week_effect = TRUE,
week_length = 7,
scale = list(),
likelihood = TRUE,
return_likelihood = FALSE
)
```

## Arguments

- family
Character string defining the observation model. Options are
Negative binomial ("negbin"), the default, and Poisson.

- phi
A numeric vector of length 2, defaults to 0, 1. Indicates the
mean and standard deviation of the normal prior used for the observation
process.

- weight
Numeric, defaults to 1. Weight to give the observed data in
the log density.

- week_effect
Logical defaulting to `TRUE`

. Should a day of the week effect
be used in the observation model.

- week_length
Numeric assumed length of the week in days, defaulting to
7 days. This can be modified if data aggregated over a period other than a week
or if data has a non-weekly periodicity.

- scale
List, defaulting to an empty list. Should an scaling factor be applied
to map latent infections (convolved to date of report). If none empty a mean
(`mean`

) and standard deviation (`sd`

) needs to be supplied defining the normally
distributed scaling factor.

- likelihood
Logical, defaults to `TRUE`

. Should the likelihood be
included in the model

- return_likelihood
Logical, defaults to `FALSE`

. Should the likelihood
be returned by the model.

## Value

A list of observation model settings.

## Examples

```
# default settings
obs_opts()
#> $family
#> [1] "negbin"
#>
#> $phi
#> [1] 0 1
#>
#> $weight
#> [1] 1
#>
#> $week_effect
#> [1] TRUE
#>
#> $week_length
#> [1] 7
#>
#> $scale
#> list()
#>
#> $likelihood
#> [1] TRUE
#>
#> $return_likelihood
#> [1] FALSE
#>
# Turn off day of the week effect
obs_opts(week_effect = TRUE)
#> $family
#> [1] "negbin"
#>
#> $phi
#> [1] 0 1
#>
#> $weight
#> [1] 1
#>
#> $week_effect
#> [1] TRUE
#>
#> $week_length
#> [1] 7
#>
#> $scale
#> list()
#>
#> $likelihood
#> [1] TRUE
#>
#> $return_likelihood
#> [1] FALSE
#>
# Scale reported data
obs_opts(scale = list(mean = 0.2, sd = 0.02))
#> $family
#> [1] "negbin"
#>
#> $phi
#> [1] 0 1
#>
#> $weight
#> [1] 1
#>
#> $week_effect
#> [1] TRUE
#>
#> $week_length
#> [1] 7
#>
#> $scale
#> $scale$mean
#> [1] 0.2
#>
#> $scale$sd
#> [1] 0.02
#>
#>
#> $likelihood
#> [1] TRUE
#>
#> $return_likelihood
#> [1] FALSE
#>
```