A call to `rw()`

can be used in the 'formula' argument of model
construction functions in the `epinowcast`

package such as `enw_formula()`

.
Does not evaluate arguments but instead simply passes information for use in
model construction.

## Usage

`rw(time, by, type = c("independent", "dependent"))`

## Arguments

- time
Defines the random walk time period.

- by
Defines the grouping parameter used for the random walk. If not specified no grouping is used. Currently this is limited to a single variable.

- type
Character string, how standard deviation of grouped random walks is estimated: "independent", or "dependent" across groups; enforced by

`base::match.arg()`

.

## Value

A list defining the time frame, group, and type with class
"enw_rw_term" that can be interpreted by `construct_rw()`

.

## See also

Functions used to help convert formulas into model designs
`as_string_formula()`

,
`construct_re()`

,
`construct_rw()`

,
`enw_formula()`

,
`enw_manual_formula()`

,
`parse_formula()`

,
`remove_rw_terms()`

,
`re()`

,
`rw_terms()`

,
`split_formula_to_terms()`

## Examples

```
rw(time)
#> $time
#> [1] "time"
#>
#> $by
#> NULL
#>
#> $type
#> [1] "independent"
#>
#> attr(,"class")
#> [1] "enw_rw_term"
rw(time, location)
#> $time
#> [1] "time"
#>
#> $by
#> [1] "location"
#>
#> $type
#> [1] "independent"
#>
#> attr(,"class")
#> [1] "enw_rw_term"
rw(time, location, type = "dependent")
#> $time
#> [1] "time"
#>
#> $by
#> [1] "location"
#>
#> $type
#> [1] "dependent"
#>
#> attr(,"class")
#> [1] "enw_rw_term"
```