R/fadeColor.R

In OpenIntroStat/openintro-r-package: Data Sets and Supplemental Functions from 'OpenIntro' Textbooks and Labs

#' Fade colors
#'
#' Fade colors so they are transparent.
#'
#'
#' @param col An integer, color name, or RGB hexadecimal.
#' @param fade The amount to fade \code{col}. This value should be a character
#' in hexadecimal from '00' to 'FF'. The smaller the value, the greater the
#' fading.
#' @author David Diez
#' @export
#' @examples
#'
#' data(mariokart)
#' new <- mariokart$cond == "new"
#' used <- mariokart$cond == "used"
#'
#' # ===> color numbers <===#
#' dotPlot(mariokart$total_pr[new],
#'   ylim = c(0, 3), xlim = c(25, 80), pch = 20,
#'   col = 2, cex = 2, main = "using regular colors"
#' )
#' dotPlot(mariokart$total_pr[used], at = 2, add = TRUE, col = 4, pch = 20, cex = 2)
#' dotPlot(mariokart$total_pr[new],
#'   ylim = c(0, 3), xlim = c(25, 80),
#'   col = fadeColor(2, "22"), pch = 20, cex = 2,
#'   main = "fading the colors first"
#' )
#' dotPlot(mariokart$total_pr[used],
#'   at = 2, add = TRUE,
#'   col = fadeColor(4, "22"), pch = 20, cex = 2
#' )
#'
#' # ===> color names <===#
#' dotPlot(mariokart$total_pr[new],
#'   ylim = c(0, 3), xlim = c(25, 80), pch = 20,
#'   col = "red", cex = 2, main = "using regular colors"
#' )
#' dotPlot(mariokart$total_pr[used], at = 2, add = TRUE, col = "blue", pch = 20, cex = 2)
#' dotPlot(mariokart$total_pr[new],
#'   ylim = c(0, 3), xlim = c(25, 80),
#'   col = fadeColor("red", "22"), pch = 20, cex = 2,
#'   main = "fading the colors first"
#' )
#' dotPlot(mariokart$total_pr[used],
#'   at = 2, add = TRUE,
#'   col = fadeColor("blue", "22"), pch = 20, cex = 2
#' )
#'
#' # ===> hexadecimal <===#
#' dotPlot(mariokart$total_pr[new],
#'   ylim = c(0, 3), xlim = c(25, 80), pch = 20,
#'   col = "#FF0000", cex = 2, main = "using regular colors"
#' )
#' dotPlot(mariokart$total_pr[used],
#'   at = 2, add = TRUE, col = "#0000FF", pch = 20,
#'   cex = 2
#' )
#' dotPlot(mariokart$total_pr[new],
#'   ylim = c(0, 3), xlim = c(25, 80),
#'   col = fadeColor("#FF0000", "22"), pch = 20, cex = 2,
#'   main = "fading the colors first"
#' )
#' dotPlot(mariokart$total_pr[used],
#'   at = 2, add = TRUE,
#'   col = fadeColor("#0000FF", "22"), pch = 20, cex = 2
#' )
#'
#' # ===> alternative: rgb function <===#
#' dotPlot(mariokart$total_pr[new],
#'   ylim = c(0, 3), xlim = c(25, 80), pch = 20,
#'   col = rgb(1, 0, 0), cex = 2, main = "using regular colors"
#' )
#' dotPlot(mariokart$total_pr[used],
#'   at = 2, add = TRUE, col = rgb(0, 0, 1),
#'   pch = 20, cex = 2
#' )
#' dotPlot(mariokart$total_pr[new],
#'   ylim = c(0, 3), xlim = c(25, 80),
#'   col = rgb(1, 0, 0, 1 / 8), pch = 20, cex = 2,
#'   main = "fading the colors first"
#' )
#' dotPlot(mariokart$total_pr[used],
#'   at = 2, add = TRUE,
#'   col = rgb(0, 0, 1, 1 / 8), pch = 20, cex = 2
#' )
fadeColor <- function(col, fade = "FF") {
  if (is.numeric(col)[1]) {
    col <- round(col)
    COL <- col
    COL[col %% 8 == 0] <- "#BBBBBB"
    COL[col %% 8 == 1] <- "#000000"
    COL[col %% 8 == 2] <- "#BB0000"
    COL[col %% 8 == 3] <- "#00FF00"
    COL[col %% 8 == 4] <- "#0000FF"
    COL[col %% 8 == 5] <- "#00FFFF"
    COL[col %% 8 == 6] <- "#FF00FF"
    COL[col %% 8 == 7] <- "#FFFF00"
    col <- COL
  } else if (substr(col[1], 1, 1) != "#") {
    temp <- grDevices::col2rgb(col[1])
    col <- grDevices::rgb(temp[1], temp[2], temp[3], maxColorValue = 255)
  }
  # check fading
  if (any(nchar(col[1]) != 7)) {
    stop("col must be either an integer or in #RRGGBB format\n")
  }
  if (any(nchar(fade[1]) != 2)) {
    stop("fade must be a hexadecimal string of 2 characters\n")
  }
  col <- paste(col, fade, sep = "")
  return(col)
}