total_tax_add.R

#' @title Summarize and add tax data
#' 
#' @description Create and add a total tax row, if there are multiple tax rows
#' present in the \code{data_table}. 
#'
#' @param data_table A SIOT, a use table, a supply table, or a margins 
#' table that has product and production tax rows in among the primary inputs.
#' @param tax_names Defaults to \code{("d21x31", "d29x39")}, 
#' which are the Eurostat 
#' names for taxes. The parameter is not case sensitive.
#' @param total_tax_name Defaults to \code{'TOTAL_TAX'}. The name of the 
#' summarized row. It is case sensitive.
#' @return A data frame with the vector of multipliers and the an 
#' auxiliary metadata column (for joining with other matrixes.)
#' @importFrom dplyr select full_join summarise mutate across
#' @family iotables processing functions
#' @examples
#' de_io <- iotable_get()
#' 
#' total_tax_add (de_io, 
#'                tax_names = c("net_tax_products",  "net_tax_production"),
#'                total_tax_name = "total_tax")
#' @export

total_tax_add <- function ( data_table, 
                            tax_names = c("d21x31", "d29x39"), 
                            total_tax_name = "TOTAL_TAX") {
  . <- NULL
  
  if(is.null(tax_names)) { 
    stop ( 'Tax names must be set.') 
    } 
  
  key_column <- tolower(as.character(unlist(data_table[,1])) )
  
  if (! all ( tax_names %in% key_column )) {
    stop ( "The tax names ", 
           paste(tax_names, collapse= ', '), 
           ' (not case sensitive) were not found in the data table.')
  }
  
  tax <- data_table [which (key_column %in% tax_names), ]
  
  tax <- summarise (tax, across(where(is.numeric), sum) ) %>%
    cbind ( data_table[1,1], .) %>%
    dplyr::mutate(across(where(is.factor), as.character))
  
  tax [ 1,1 ] <- total_tax_name
  
  names (tax)[1] <- names (data_table)[1]
  
  siot_ext   <- full_join ( 
    mutate(data_table, across(where(is.factor), as.character)), tax,
    by = names (tax) )
  
  if ( any(c("final_consumption_households", "p3_s14") %in% tolower ( names ( siot_ext)))  ) {
    household_col <- which ( tolower ( names ( siot_ext)) %in% c("final_consumption_households", "p3_s14") )
    new_row <- which ( tolower ( as.character(siot_ext[,1])) %in% total_tax_name )
    
    siot_ext[new_row, household_col] <- ifelse ( test = is.na(siot_ext[new_row, household_col]), 
                                                 yes  = 0, 
                                                 no   = siot_ext[new_row, household_col]) 
    } #end of households case 
  
  siot_ext  
}