R/setup.x.matrix.R

In bensoltoff/ZeligBLME: A Zelig Model

#' Setup Matrix
#' @note This function is used internally by \code{mixed.zelig}
#' @param form a \code{formula} whose "fixed" terms are used to generate
#'   a matrix for simulating quantities of itnerest
#' @param x a \code{setx} object
#' @return a \code{matrix}
#' @author Matt Owen \email{mowen@@iq.harvard.edu}
setup.x.matrix <- function(form, x) {
  
  # Error-catching
  if (is.null(x))
    return(NULL)
  
  parsed.formula <- .getRandAndFixedTerms(form)
  untagged.vars <- all.vars(parsed.formula$fixed)
  
  # Get only the explanatory parameters from
  # the x-matrix
  x.matrix <- x$updated[untagged.vars]
  
  x.matrix <- model.matrix(parsed.formula$fixed, data=x$updated[untagged.vars])
  
  x.matrix
}