R/z.R

In IQSS/Zelig4: Everyone's Statistical Software

#' Return value for a zelig2-function
#'
#' This is an API-function that bridges a model-fitting function with a zelig
#' interface.
#' @note This is used internally by Zelig-dependent packages to instruct Zelig
#' how to evaluate the function call to a particular statistical model.
#' @param .function a function
#' @param ... a set of parameters to be evaluated symbolically
#' @return a ``z'' object which specifies how to evaluate the fitted model
#' @export
z <- function (.function, ..., .hook = NULL) {
  # Construct the function call
  .call <- as.call(as.list(match.call())[-1])
  .function.name <- as.character(.call[[1]])
  .parent <- parent.frame()
  .dots <- list(...)

  # Ensure that hook works appropriately
  if(!missing(.hook)) {
    if (!is.function(.hook)) {
      warning(".hook parameter must be a function. ignoring.")
      .hook <- NULL
    }
  }

  s <- append(list(as.name(.function.name)), list(...))
  literal.call <- as.call(s)

  # Construct the object
  s <- list(
            "function" = .function,
            "hook" = .hook,

            "call" = .call,
            "env" = .parent,

            "function.name" = .function.name,
            "dots" = .dots,

            "literal.call" = literal.call
            )

  # Set attributes
  attr(s, 'baseenv') <- baseenv()
  attr(s, 'call') <- match.call()
  attr(s, 'function') <- substitute(.function)

  # Set the class
  class(s) <- 'z'

  # Return
  s
}