#' Emulates the jet colormap from Matlab
#'
#' @param n the number of levels in the colormap;
#' the default is 64
#' @return an rgb vector of length n
#' @examples
#' plot(1:64, col=jet.colors(64))
#' @export
jet.colors <- function(n = 64){
## JET.COLORS(n)
## Defines a jet colormap (blue is low, red is high) with
## n levels. Returns an n by 3 matrix of rgb values.
k <- ceiling(n/4);
temp.red <- c(rep(0, 2*k), 1:k, rep(k, k-1), k:1);
temp.green <- c(rep(0, k), 1:k, rep(k, k-1), k:1, rep(0, k));
temp.blue <- c(1:k, rep(k, k-1), k:1, rep(0, 2*k));
temp.rgb <- cbind(temp.red, temp.green, temp.blue);
delta <- 5 * k - 1 - n;
delta <- ceiling(delta/2);
temp.rgb <- temp.rgb[delta:(delta + n - 1),] / k;
## assemble everything; last value is returned
jet.colors <-
rgb(temp.rgb[,1], temp.rgb[,2], temp.rgb[,3]);
}
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