R/SAR.R

In iwaqr: Irrigation Water Quality Assessment and Visualizations

#' Sodium Adsorption Ratio (SAR) Calculation
#'
#' @param df Dataframe containing necessary variables (Na, Ca, Mg, K).
#' @param convert_to_meq Logical, indicating whether to convert concentrations to meq/L (default: TRUE).
#' @return SAR value.
#'
SAR <- function(df, convert_to_meq = TRUE) {
  # Conversion factors for mg/L to meq/L
  conversion_factor_Na <- 1 / 22.98
  conversion_factor_Ca <- 1 / 20.04
  conversion_factor_Mg <- 1 / 12.16
  conversion_factor_K <- 1 / 39.1

  # Apply conversion if requested
  if (convert_to_meq) {
    df$Na <- df$Na * conversion_factor_Na
    df$Ca <- df$Ca * conversion_factor_Ca
    df$Mg <- df$Mg * conversion_factor_Mg
    df$K <- df$K * conversion_factor_K
  }

  # SAR calculation
  sar_value <- (df$Na) / sqrt((df$Ca + df$Mg)/2)
  return(sar_value)
}