hlm: Inference for a Heteroscedastic Linear Model

#' Dataset of colon cancer deaths.
#'
#' Survival times of patients in the chemotherapy colon cancer study of Laurie (1989).  This is a subset of the \code{colon} dataset from the \pkg{survival} package.
#'
#' @format A data frame with 888 rows and 13 variables:
#' \describe{
#'   \item{time}{Survival time (in days).}
#'   \item{status}{Survival time status: Observed (\code{TRUE}), Right-censored (\code{FALSE}).}
#'   \item{rx}{Treatment type: Control (\code{obs}), Levamisole (\code{Lev}), Levamisole + Fluorouracil (\code{Lev+5FU}).}
#'   \item{sex}{Sex of patient (\code{female}/\code{male}).}
#'   \item{age}{Age of patient (in years).}
#'   \item{obstruct}{Obstruction of colon by tumor (T/F).}
#'   \item{perfor}{Perforation of colon (T/F).}
#'   \item{adhere}{Adherence of tumor to nearby organs (T/F).}
#'   \item{nodes}{Number of lymph nodes with detectable cancer (integer betwwen 0-33).}
#'   \item{differ}{Differentiation index of tumor: \code{well}, moderate (\code{moder}), \code{poor}.}
#'   \item{extent}{Extent of local spread: submucosa (\code{submuc}), muscle, serosa, contiguous structures (\code{cstruct}).}
#'   \item{surg}{Time from surgery to registration (\code{short}, \code{long}).}
#'   \item{node4}{More than 4 positive lymph nodes (T/F).}
#' }
#' @source Subset of the \code{colon} dataset from the \pkg{survival} package.
#' @references Laurie, J.A., Moertel, C.G., Fleming, T.R., Wieand, H.S., Leigh, J.E., Rubin, J., McCormack, G.W., Gerstner, J.B., Krook, J.E., and Malliard, J. "Surgical adjuvant therapy of large-bowel carcinoma: An evaluation of levamisole and the combination of levamisole and fluorouracil: The North Central Cancer Treatment Group and the Mayo Clinic".  \emph{Journal of Clinical Oncology} 7:10 (1989): 1447-1456.  \url{https://www.ncbi.nlm.nih.gov/pubmed/2778478}
"colond"