Dark.Rcheck/00_pkg_src/Dark/R/P3.R

In emkayoh/Dark: The Analysis of Dark Adaptation Data

#' @export 

P3 <- function(a, X) {
  # a simple exponential decay
  x <- .GlobalEnv$x
  y <- .GlobalEnv$y # explicitly locating the values
  if (missing(X)) {
    if (length(a) == 1) {
      list(Pn = 3, Mod = "P3")
    } else {
      sum((y - (a[1] + a[2] * exp(-x / a[3]))) ^ 2)
    }
  } else {
    a[1] + a[2] * exp(-X / a[3])
  }

}