R/vis_palette.R

In adamhsparks/theme_usq: USQ Themed Plots for Base Graphics and 'ggplot2'

#' Visualise a single palette using R's graphics capabilities
#'
#' Display a single palette to see whether it meets your needs.
#' If no \code{num} parameter is given, all the colours in the palette will be
#' displayed.
#' If \code{num} is less than the number of colours in the palette,
#' then only the first \code{num} colours will be displayed.
#' If \code{num} is greater than the number of colours in the palette,
#' then that many colours will be generated by linear interpolation over the
#' vector of colours in the chosen palette.
#' @param pal character, vector of (hexadecimal) colours representing a palette
#' @param ttl character, title to be displayed (the name of the palette)
#' @param num numeric, the number of colours to display
#' @examples
#' vis_palette(usq_palettes$primary)
#' vis_palette(usq_palettes$bright, "bright")
#' vis_palette(usq_palettes$primary, "primary 4", num = 4)
#' vis_palette(usq_palettes$primary, "primary interpolated to 25", num = 25)
#'
#' @export
#'

vis_palette <-
  function(pal,
           ttl = deparse(substitute(pal)),
           num = length(pal)) {
    if (num <= 0)
      stop("'num' should be > 0")
    pal_func <- grDevices::colorRampPalette(pal)
    graphics::image(
      seq_len(num),
      1,
      as.matrix(seq_len(num)),
      col = pal_func(num),
      main = paste0(ttl, " (", length(pal),
                    " colours in palette, ",
                    num,
                    " displayed)"),
      xlab = "",
      ylab = "",
      xaxt = "n",
      yaxt = "n",
      bty = "n"
    )
  }