R/relweights_helpers.R

In Stan125/vibe: Variable Importance Beyond Linear Models

#' @title Null model fitter
#'
#' @description
#' Fits a null model (model without any explanatory variables).
#'
#' @param object Model object, one of the ones supported in [scam]
#' @param ... Other arguments
#'
#' @return a fitted model object
#' @export
#'
fit_null_model <- function(object, ...) {
  UseMethod("fit_null_model", object)
}

#' @importFrom stats family glm
#' @rdname fit_null_model
#' @export
fit_null_model.glm <- function(object, ...) {
  depvar <- object$y
  fam <- family(object)
  mod <- glm(depvar ~ 1, family = fam)
  return(mod)
}

#' @importFrom stats family
#' @importFrom mgcv gam
#' @rdname fit_null_model
#' @export
fit_null_model.gam <- function(object, ...) {
  depvar <- object$y
  fam <- family(object)
  mod <- gam(depvar ~ 1, family = fam)
  return(mod)
}

#' @importFrom stats family
#' @importFrom gamlss gamlss
#' @rdname fit_null_model
#' @export
fit_null_model.gamlss <- function(object, ...) {
  depvar <- object$y
  fam <- family(object)
  if (length(fam) > 1) {
    fam <- fam[1]
  }
  mod <- gamlss(depvar ~ 1, family = fam, trace = FALSE)
  return(mod)
}