R/pal_rainbow.R

In espadon: Easy Study of Patient DICOM Data in Oncology

#' Rainbow palette
#' @description The \code{pal.rainbow} function produces a color palette adapted 
#' to dose representation.
#' @param n Integer, number of colors to be in the palette
#' @param alpha Vector representing the opacity, in the range of 0 (transparent) 
#' to 1 (opaque). If \code{alpha = NULL}, all colors are opaque.
#' @return Returns a color-labeled vector of size \code{n}.
#' @examples
#' pal <- pal.rainbow(255)
#'
#' image(x = seq(0, 70, length.out = 255), y = 1,
#'       z = matrix(seq(0, 70, length.out = 255), ncol = 1),
#'       col = pal,
#'       main = "Rainbow colors")

#' @export

pal.rainbow <- function(n, alpha = seq(0.8, 0, length.out = n)) {
  if (n < 2) stop("n must be >1")
  if (is.null(alpha)) alpha = rep(1, n)
  pal <- rainbow(n, s = seq(1, 0, length.out = n),
                 start = 0, end = 4 / 6,
                 alpha = alpha,
                 rev = TRUE)
  attr(pal,"label") = "rainbow"
  return(pal)
}