Make all arguments (except method and data) optional

[RoelBrouwer]

No description provided.

[chStaiger]

@hanneoberman and @stefvanbuuren
We have a problem with the mice function not accepting NULL for the parameters m, seed and maxit.

> mice(nhanes, m=NULL)
Error: Argument m not numeric
> mice(nhanes, seed=NULL)
Error in if (!is.na(seed)) set.seed(seed) : argument is of length zero
> mice(nhanes, maxit=NULL)
Error in array(NA, dim = c(length(varnames), maxit, m)) :
  negative length vectors are not allowed

Because of that we currently hard-coded their values if they are not given in the API call. And of course we risk that the HTTP API will not be synchronised automatically when those values get updated.

Is it possible to
Option 1) Allow for NULL as a value for the three parameters
or
Option 2) have a mice::get_defaults(var_name) function with which we can retrieve the current default values
?

[stefvanbuuren]

Would something like this work?

get_defaults <- function(m, maxit, seed) {
  m <- ifelse(is.null(m), 5, m)
  maxit <- ifelse(is.null(maxit), 5, maxit)
  seed <- ifelse(is.null(seed), NA, seed)
  list(m = m, maxit = maxit, seed = seed)
}

get_defaults(NULL, NULL, NULL)
#> $m
#> [1] 5
#> 
#> $maxit
#> [1] 5
#> 
#> $seed
#> [1] NA
get_defaults(m = NULL, maxit = NULL, seed = NULL)
#> $m
#> [1] 5
#> 
#> $maxit
#> [1] 5
#> 
#> $seed
#> [1] NA

^{Created on 2023-11-24 with reprex v2.0.2}

[chStaiger]

That looks great. We can also drop the parameters for the function if the return value is a named list with all parameters with a preset value.

[stefvanbuuren]

Perhaps the function get_defaults() could be improved by returning an alist instead of a list. That would make it easier to work with formals() and do.call().