R/cherry_model.R

In RPertille/ChillModels: Processing Chill and Heat Models for Temperate Fruit Trees

#' @title Sweet Cherry Model
#' @name cherry_model
#' @description Quantifies the chill accumulation by means of converting temperatures to chill-units.
#' @param x Vector containing temperature values (Celsius-degree).
#' @param total TRUE Shows the total value of accumulation, FALSE shows the value of chill-unit for each temperature (TRUE is default).
#' @details The model is based on chill-units, where 1 chill-unit is when the tree is exposure between -2.1°C and 7°C. When the temperature is above 18°C the chill-unit is -1. The chill-units accumulation is 0 when occurs temperature between 14°C and 16°C.
#' @note This model was make for quantifying the chill accumulation rates to 'Sweetheart' Sweet Cherry. We aren't recommended the apliccation for others species.
#' @return The function returns values the chill-units for each temperature of vector (Total = FALSE), or returns the chill-units accumulation (Total = TRUE).
#' @examples 
#' 
#' x <- rnorm(500, 8, 7)
#' cherry_model(x)
#' cherry_model(x, FALSE)
#' 
#' @references GUAK, Sunghee & NEILSEN, Denise. (2013). Chill Unit Models for Predicting Dormancy Completion of Floral Buds in Apple and Sweet Cherry.
#' @importFrom utils tail
#' @export


cherry_model <- function(x, total=TRUE){
  
  t <- c(-2.1,7,8,10,13,16,18)
  v <- c(0,1,0.75,0.5,0.25,0,-0.5,-1) 
  
  y <- rep(v[8], length(x))
  y[which(x<=t[1])] <- v[1]
  y[which(x>t[1] & x<=t[2])] <- v[2]
  y[which(x>t[2] & x<=t[3])] <- v[3]
  y[which(x>t[3] & x<=t[4])] <- v[4]
  y[which(x>t[4] & x<=t[5])] <- v[5]
  y[which(x>t[5] & x<=t[6])] <- v[6]
  y[which(x>t[6] & x<=t[7])] <- v[7]
  
  if (total==TRUE) 
    return(tail(cumsum(y),n=1))
  else return(y)
}