xlik: Internal function used by xreg
In intelligentaccident/xreg: Flexible maximum likelihood-based regression

Allows a list of formulas and fitting functions to be used for each type or set of data.

xlik(
  ...,
  controlList,
  dataList,
  print_sum = FALSE,
  return_lik_df = FALSE,
  return_first_df = FALSE,
  latent_classes = 0,
  latent_class_parameters = character()
)

`...`	optional arguments to be forwarded to x_mle, optim, xregControl, etc.
`controlList`	one or more xregControl-objects (concatenated using c() ) to control maximum-likelihood estimation for different types or sets of data provided in dataList. Can alternatively provide a single formula or list of formulas, in which case an xregControl object will be generated on the fly. An xreg-object can be provided, in which case the xregControlList will be extracted. See examples
`dataList`	Named list of data.frames for which maximum sum-likelihood should be estimated. Names must correspond to names of xregControl objects. If no names are provided, order will be used to decide which xregControl-object to use.
`print_sum`	Optional argument to force continuous printing of the progress of fitting. Can be useful for debugging.
`return_lik_df`	if true, will return the data.frame(s) on which likelihood are estimated
`return_first_df`	if true, eill return the first fit to initial values
`latent_classes`	Optional integer parameter defining the number of latent classes to be fitted
`latent_class_parameter`	Optional character vector with names corresponding to the parameters that are to be varied in the latent classes (if latent_classes > 1)