Add roxygen2 documentation to update_possible_subj_data function

Co-authored-by: d-morrison <2474437+d-morrison@users.noreply.github.com>

Author: Copilot

R/update_possible_subj_data.R

@@ -1,3 +1,41 @@
+#' Update subject-level data with posterior probabilities
+#'
+#' Internal helper function that updates subject-level data by computing
+#' various conditional probabilities used in the EM algorithm for
+#' fitting the joint model. This function combines observation-level
+#' predictions with participant-level data and omega estimates to compute
+#' posterior probabilities needed for parameter estimation.
+#'
+#' @param obs_data_possibilities A [data.frame] containing all possible
+#'   observation-level data combinations, including ID, S (possible
+#'   seroconversion dates), and Y (MAA classifications).
+#' @param MAA_model A fitted [stats::glm()] model object used to predict
+#'   P(Y=1|T=t), the probability of MAA-positive status given time since
+#'   seroconversion.
+#' @param participant_level_data A [data.frame] containing participant-level
+#'   information, including ID, Stratum, and P(S>=l|E=e) (the probability
+#'   that seroconversion occurs on or after the last negative test date).
+#' @param omega_hat A [data.frame] containing estimated parameters for the
+#'   seroconversion date distribution model, including S, Stratum, P(S=s|S>=s,E=e),
+#'   and P(S>s|S>=s,E=e).
+#'
+#' @returns A [data.frame] containing updated subject-level data with the
+#'   following columns:
+#' \itemize{
+#'   \item `ID`: Participant identifier
+#'   \item `Stratum`: Stratification variable
+#'   \item `S`: Possible seroconversion date
+#'   \item `P(Y=y|T=t)`: Probability of observed MAA outcomes given time since
+#'     seroconversion
+#'   \item `P(S=s|E=e)`: Marginal probability of seroconversion at time s given
+#'     enrollment date
+#'   \item `P(S=s|e,l,r,o,y)`: Posterior probability of seroconversion at time s
+#'     given all observed data (used to estimate omega and theta)
+#'   \item `P(S>=s|e,l,r,o,y)`: Posterior probability that seroconversion occurs
+#'     on or after time s (used to estimate omega)
+#' }
+#'
+#' @keywords internal
 update_possible_subj_data <- function(
     obs_data_possibilities,
     MAA_model,