survival_helpers.R

#' Helper Functions for Survival Analysis
#'
#' Handles the W (covariates), A (treatment/intervention), T_tilde (time-to-event),
#' Delta (censoring indicator), t_max (the maximum time to estimate) survival data structure
#'
#' @param data a \code{data.frame}, or \code{data.table} containing data for use in estimation
#' @param node_list a list of character vectors, listing the variables that comprise each node
#' @param variable_types a list of variable types, one for each node. If missing, variable types will be guessed
#' @param tmle_task a \code{\link{tmle3_Task}} as constructed via \code{survival_tx_task}
#' @param learner_list a list of sl3 learners, one for A and one for Y to be used for likelihood estimation
#' @param ... extra arguments.
#' @export
#' @rdname survival_tx
survival_tx_npsem <- function(node_list, variable_types = NULL) {
  # make the tmle task

  # define censoring (lost to followup node)
  censoring <- define_node("pre_failure", node_list$pre_failure, c())
  npsem <- list(
    # TODO: causal relation, handle t_max
    define_node("W", node_list$W, variable_type = variable_types$W),
    define_node("A", node_list$A, c("W"), variable_type = variable_types$A),
    define_node("T_tilde", node_list$T_tilde, c("A", "W"), variable_type = variable_types$T_tilde),
    define_node("Delta", node_list$Delta, variable_type = variable_types$Delta),
    censoring,
    # TODO: remove t parent, handle in get_regression
    define_node("N", node_list$N, c("A", "W"), variable_type = variable_types$N, censoring_node = censoring),
    define_node("A_c", node_list$A_c, c("A", "W"), variable_type = variable_types$A_c, censoring_node = censoring)
  )

  return(npsem)
}

#' @export
#' @rdname survival_tx
survival_tx_task <- function(data, node_list, variable_types = NULL, ...) {
  setDT(data)

  npsem <- survival_tx_npsem(node_list, variable_types)

  if (!is.null(node_list$id)) {
    tmle_task <- tmle3_Task$new(data, npsem = npsem, id = node_list$id, time = node_list$time, ...)
  } else {
    tmle_task <- tmle3_Task$new(data, npsem = npsem, ...)
  }

  return(tmle_task)
}

#' @export
#' @rdname survival_tx
survival_tx_likelihood <- function(tmle_task, learner_list) {
  # covariates
  # TODO: whether remove duplicates for LF_emp
  W_factor <- define_lf(LF_emp, "W")

  # TODO: check if necessary
  # treatment (bound likelihood away from 0 (and 1 if binary))
  A_type <- tmle_task$npsem[["A"]]$variable_type
  if (A_type$type == "continous") {
    A_bound <- c(1 / tmle_task$nrow, Inf)
  } else if (A_type$type %in% c("binomial", "categorical")) {
    A_bound <- 0.025
  } else {
    A_bound <- NULL
  }

  A_factor <- define_lf(LF_fit, "A", learner = learner_list[["A"]], bound = A_bound)

  # TODO: modify get_regression_task and LF_fit for time variance
  # TODO: whether need bound
  outcome_bound <- 0.025
  N_factor <- define_lf(LF_fit, "N",
    learner = learner_list[["N"]],
    is_time_variant = TRUE, bound = outcome_bound,
    type = "mean"
  )
  A_c_factor <- define_lf(LF_fit, "A_c",
    learner = learner_list[["A_c"]],
    is_time_variant = TRUE, bound = outcome_bound,
    type = "mean"
  )
  # N_factor <- define_lf(LF_fit, "N", learner = learner_list[["N"]],
  #                       is_time_variant = TRUE,
  #                       type = "mean")
  # A_c_factor <- define_lf(LF_fit, "A_c", learner = learner_list[["A_c"]],
  #                         is_time_variant = TRUE,
  #                         type = "mean")

  factor_list <- list(W_factor, A_factor, N_factor, A_c_factor)

  # TODO: check
  likelihood_def <- Likelihood$new(factor_list)
  likelihood <- likelihood_def$train(tmle_task)
  return(likelihood)
}