R/RelativeWaterContent.R

In pvldcurve: Simplifies the Analysis of Pressure Volume and Leaf Drying Curves

#' Relative Water Content (RWC)
#'
#' Calculates relative water content (RWC, \%)
#'
#' @param data data frame with columns of equal length containing at least columns with the fresh weight (g),
#' the dry weight (g) and the saturated fresh weight (g)
#' @param fresh.weight optional name of the column in data containing
#' the numeric fresh weight values (g); default: "fresh.weight"
#' @param dry.weight optional name of the column in data containing
#' the numeric dry weight values (g); default: "dry.weight"
#' @param fresh.weight.saturated optional name of the column in data containing
#' the numeric saturated fresh weight values (g); default: "fresh.weight.saturated"
#' @details Relative water content (\%) is calculated as:
#' \deqn{RWC = 100 * ((FW - DW) (FWs - DW)^-1)}
#' whereas FW = fresh weight, DW = dry weight and FWs = fresh weight at water saturation.
#' @return the original data frame extended by a numeric column with the relative water content (RWC) (\%).
#' @examples
#' # get example data
#' df <- leaf_drying_data
#'
#' # extend df by RWC
#' df_with_RWC <- RelativeWaterContent(df)
#'
#' @import ggplot2
#' @importFrom graphics legend
#' @importFrom stats approx coef confint lm na.omit nls
#'
#' @export

RelativeWaterContent <- function(data,
                                 fresh.weight = "fresh.weight",
                                 dry.weight = "dry.weight",
                                 fresh.weight.saturated = "fresh.weight.saturated") {
  # check validity of data
  data_in <-
    ValidityCheck(
      data,
      fresh.weight = fresh.weight,
      dry.weight = dry.weight,
      fresh.weight.saturated = fresh.weight.saturated
    )



  # calculate RWC
  RWC <- ((data_in[[fresh.weight]] - data_in[[dry.weight]]) /
            (data_in[[fresh.weight.saturated]] - data_in[[dry.weight]])) * 100


  return(data.frame(data, RWC))
}