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#' @title
#' Generate a vector of `n` contiguous colours, as a red-yellow-green palette.
#'
#' @description
#' Takes a numeric value `n` and returns a character vector of colour HEX codes
#' corresponding to the heat map palette.
#'
#' @param n the number of colors (>= 1) to be in the palette.
#' @param alpha an alpha-transparency level in the range of 0 to 1
#' (0 means transparent and 1 means opaque)
#' @param rev logical indicating whether the ordering of the colors should be
#' reversed.
#'
#' @examples
#' barplot(rep(10, 50), col = heat_colours(n = 50), border = NA)
#'
#' barplot(rep(10, 50), col = heat_colours(n = 50, alpha = 0.5, rev = TRUE),
#' border = NA)
#'
#' @family Support
#'
#' @return
#' A character vector containing the HEX codes and the same length as `n` is
#' returned.
#'
#' @export
heat_colours <- function (n, alpha, rev = FALSE) {
## Move from red to green
pre_h <- seq(from = 0, to = 0.3, length.out = n - 1)
h <- c(1, pre_h)
## Less bright
s <- rep(0.69, length(h))
## Increasingly low value (darker)
v <- seq(from = 1, to = 0.8, length.out = n)
cols <- grDevices::hsv(h = h, s = s, v = v, alpha = alpha)
if(rev){
rev(cols)
} else if(rev == FALSE) {
cols
}
}
#' @rdname heat_colours
#' @export
heat_colors <- heat_colours
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