#' VitD: cohort data on vitamin D and mortality
#'
#' This dataset is mirrored from the \pkg{ivtools} package (version 2.3.0).
#' The upstream documentation notes the data originate from a real cohort study
#' and were modified for public availability.
#'
#' @format A data frame with variables:
#' * `age` : Age at baseline
#' * `filaggrin` : Indicator of filaggrin mutation
#' * `vitd` : Serum 25-OH-D (nmol/L) at baseline
#' * `time` : Follow-up time
#' * `death` : Death indicator during follow-up
#' @source Mirrored from \pkg{ivtools} (LGPL (>= 3)).
#' @references Sjolander, Arvid and Martinussen, Torben. "Instrumental Variable Estimation with the R Package ivtools" Epidemiologic Methods, vol. 8, no. 1, 2019, pp. 20180024.
#' @usage data(VitD)
"VitD"
