R/ei_index.R

In ideanet: Integrating Data Exchange and Analysis for Networks ('ideanet')

#' Krackhardt and Stern’s E-I Index (\code{ei_index})
#'
#' @description Linear transformation of the proportion homophilous measure (Krackhardt and Stern 1988; Perry et al. 2018)
#'
#' @param ego_id A vector of unique ego identifiers located in an ego dataframe. If using data objects created by \code{\link{ego_netwrite}}, this should be the data frame entitled \code{egos}.
#' @param ego_measure A vector of attributes corresponding to each ego
#' @param alter_ego A vector of ego identifiers located in an alter dataframe. If using data objects created by \code{\link{ego_netwrite}}, this should be the data frame entitled \code{alters}.
#' @param alter_measure A vector of attributes corresponding to each alter
#' @param prefix A character value indicating the desired prefix for the calculated E-I measure
#' @param suffix A character value indicating the desired suffix for the calculated E-I measure
#'
#' @return \code{ei_index} returns a dataframe of vectors that include the ego identifier and the ei-index value for the selected attribute
#'
#' @export
#'
#' @importFrom rlang .data
#'
#' @examples
#'
#'# Run `ego_netwrite`
#'ngq_nw <- ego_netwrite(egos = ngq_egos,
#'                       ego_id = ngq_egos$ego_id,
#'
#'                       alters = ngq_alters,
#'                       alter_id = ngq_alters$alter_id,
#'                       alter_ego = ngq_alters$ego_id,
#'
#'                       max_alters = 10,
#'                       alter_alter = ngq_aa,
#'                       aa_ego = ngq_aa$ego_id,
#'                       i_elements = ngq_aa$alter1,
#'                       j_elements = ngq_aa$alter2,
#'                       directed = FALSE)
#'
#'
#'# Calculate E-I Index for Race
#'race_ei <- ei_index(ego_id = ngq_nw$egos$ego_id, ego_measure = ngq_nw$egos$race,
#'                    alter_ego = ngq_nw$alters$ego_id, alter_measure = ngq_nw$alters$race,
#'                    prefix = "race")
#'
#'race_ei


ei_index <- function(ego_id,
                     ego_measure,
                     alter_ego,
                     alter_measure,
                     prefix = NULL,
                     suffix = NULL) {

  ego_df <- data.frame(ego_id = ego_id,
                       ego_val = ego_measure)
  alter_df <- data.frame(ego_id = alter_ego,
                         alter_val = alter_measure)

  var_df <- dplyr::left_join(alter_df, ego_df, by = "ego_id")

  ei_df <- var_df %>%
    dplyr::group_by(ego_id) %>%
    dplyr::summarize(length = dplyr::n(),
                     num_sim = sum(as.character(.data$alter_val) == as.character(.data$ego_val), na.rm = TRUE),
                     prop_sim = .data$num_sim/length,
                     num_diff = sum(as.character(.data$alter_val) != as.character(.data$ego_val), na.rm = TRUE),
                     prop_diff = .data$num_diff/length,
                     ei_index = (.data$prop_diff - .data$prop_sim)/length) %>%
    dplyr::ungroup() %>%
    dplyr:: select(ego_id, ei_index)


  if (!is.null(prefix)) {
    colnames(ei_df) <- paste(prefix, colnames(ei_df), sep = "_")
    colnames(ei_df)[[1]] <- "ego_id"
  }

  if (!is.null(suffix)) {
    colnames(ei_df) <- paste(colnames(ei_df), suffix, sep = "_")
    colnames(ei_df)[[1]] <- "ego_id"
  }

  return(ei_df)

}