R/meta_split.R

In metalite: ADaM Metadata Structure

# Copyright (c) 2023 Merck & Co., Inc., Rahway, NJ, USA and its affiliates.
# All rights reserved.
#
# This file is part of the metalite program.
#
# metalite is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

#' Split metadata into groups
#'
#' @inheritParams define_plan
#' @param by A character variable name both in
#'   population level and observation level data of a metadata object.
#'
#' @return A metadata object split by the input variable.
#'
#' @export
#'
#' @examples
#' meta_example() |> meta_split("RACE")
meta_split <- function(meta, by) {
  meta_check_var(meta, by)

  pop <- meta$data_population
  obs <- meta$data_observation

  pop_by <- split(pop, pop[[by]])
  obs_by <- split(obs, obs[[by]])

  res <- list()
  for (i in 1:length(pop_by)) {
    res[[i]] <- meta
    res[[i]]$data_population <- pop_by[[i]]
    res[[i]]$data_observation <- obs_by[[i]]
  }
  names(res) <- names(pop_by)

  res
}