R/mod.edgescorr.R

In statnet/EpiModelHIVhet: EpiModel for HIV-1 Infection among Heterosexual Couples in Sub-Saharan Africa

#' @title Adjustment for the Edges Coefficient with Changing Network Size
#'
#' @description Adjusts the edges coefficients in a dynamic network model
#'              to preserve the mean degree.
#'
#' @inheritParams aging_het
#'
#' @details
#' In HIV/STI modeling, there is typically an assumption that changes in
#' population size do not affect one's number of partners, specified as the
#' mean degree for network models. A person would not have 10 times the number
#' of partners should he move from a city 10 times as large. This module uses
#' the adjustment of Krivitsky et al. to adjust the edges coefficients on the
#' three network models to account for varying population size in order to
#' preserve that mean degree.
#'
#' @return
#' The network model parameters stored in \code{dat$nwparam} are updated.
#'
#' @references
#' Krivitsky PN, Handcock MS, and Morris M. "Adjusting for network size and
#' composition effects in exponential-family random graph models." Statistical
#' Methodology. 2011; 8.4: 319-339.
#'
#' @keywords module
#' @export
#'
edges_correct_het <- function(dat, at) {

  # Popsize
  old.num <- dat$epi$num[at - 1]
  new.num <- sum(dat$attr$active == 1, na.rm = TRUE)

  # New Coefs
  coef.form <- get_nwparam(dat)$coef.form
  coef.form[1] <- coef.form[1] + log(old.num) - log(new.num)
  dat$nwparam[[1]]$coef.form <- coef.form

  return(dat)
}