R/colr.R

In JVAdams/GLFC: Great Lakes Fishery Commission

#' Create a Range of Colors
#'
#' Create a range of colors between two specified colors.
#' @param x
#'   A numeric vector, the values to be assigned colors.
#' @param fromcolname
#'   A character or numeric scalar, indicating the color to use for the
#'   lowest value in \code{x}.
#'   Either a color name (as listed by \code{\link{colors}()},
#'   a hexadecimal string of the form "#rrggbb" or "#rrggbbaa"
#'   (see \code{\link{rgb}}), or a positive integer i meaning
#'   \code{\link{palette}()[i]}.
#' @param tocolname
#'   A character or numeric scalar, indicating the color to use for the highest
#'   value in \code{x}. See \code{fromcolname}.
#' @export
#' @importFrom plotrix rescale
#' @seealso
#'   \code{\link{colors}}, \code{\link{palette}}.
#' @examples
#' x <- 1:10
#' plot(x, x, pch=16, col=colr(x, "blue", "yellow"), cex=4)

colr <- function(x, fromcolname, tocolname) {
  # recode x to a specified color range
  from <- col2rgb(fromcolname)
  to <- col2rgb(tocolname)
  red <- plotrix::rescale(x, c(from[1], to[1]))
  green <- plotrix::rescale(x, c(from[2], to[2]))
  blue <- plotrix::rescale(x, c(from[3], to[3]))
  rgb(red, green, blue, maxColorValue=255)
}