R/plantcoupmodel.R

In pschmidtwalter/brook90r: Run the LWF-Brook90 hydrological model from within R.

#' Interpolate plant properties using the 'Coupmodel' method.
#'
#' Creates a daily sequence for one year from parameters
#'
#' @param minval minimum value
#' @param maxval maximum value
#' @param doy.incr date (day of year) when increasing to maxval begins
#' @param doy.max  date (day of year) when maxval is reached
#' @param doy.min date (day of year) when minval is reached
#' @param shape.incr shape parameter of the increasing phase
#' @param shape.decr shape parameter of the decreasing phase
#' @param maxdoy length of the year, 366 for leap years, 365 for normal years
#'
#' @return
#'
#' @examples
#' plot(plant.coupmodel(0,5, 121, 200, 280, 0.3, 3, 365))
plant.coupmodel <- function(minval,
                            maxval,
                            doy.incr,
                            doy.max,
                            doy.min,
                            shape.incr,
                            shape.decr,
                            maxdoy) {

  inddays <- c(1,doy.incr,doy.max,doy.min,maxdoy)
  values <- c(minval, minval,maxval,minval,minval)

  forms <- c(1,shape.incr,shape.decr,1)

  ind <- c(rep(1, doy.incr), rep(2, doy.max-doy.incr),
              rep(3, doy.min-doy.max), rep(4,maxdoy-doy.min))

  doy <- 1:maxdoy

  alpha <-  sin(
    (doy - inddays[ind]) /  (inddays[ind+1] - inddays[ind]) * pi / 2) ^ (forms[ind])

  (1 - alpha)*values[ind] + alpha * values[ind+1]

}