R/displayPalette.R

In department-for-transport/dftplotr: Functions to Produce Charts in the DfT Style

#' Displays a visual colour chart of a selected palette based on the name of the palette.
#'
#' Current DfT palettes available are main.palette, electric.brights, just.beachy, cycling.hills, mountain.train and clear.skies.
#'
#' All palettes are available as either pre-set palettes of colours, or as gradients. Gradient palettes allow the user to select as many colour options as they like using the dots argument.
#'
#' @export
#' @name display_palette
#' @param palette string, name of palette of interest
#' @param gradient boolean to indicate whether palette should be standard colours or gradient. Default is gradient = FALSE
#' @param ... Additional arguments to pass to the extract_gradient function, such as number of colours to display in gradient palette
#' @title Displays a visual colour chart of a selected palette
#' @import ggplot2
#' @examples #Simple display of DfT palette example
#' display_palette(palette = "just.beachy")
#' @examples #Simple display of DfT gradient palette example
#' display_palette(palette = "just.beachy", gradient = TRUE)
#' @examples #Display of DfT gradient palette with specified length
#' display_palette(palette = "just.beachy", gradient = TRUE, n = 7)

display_palette <- function(palette, gradient = FALSE, ...){

  #Stop and list palette names if not expected variable
  if(!palette %in% names(dft.palettes)){
    stop(paste(palette, "is not a recognised DfT palette. Available palettes are: ",
               paste(names(dft.palettes), collapse = ", ")))
  }

  ##Select gradient or palette
  if(gradient){
    x <- extract_gradient(palette = palette, ...)
  }else{
    x <- dft.palettes[[palette]]
  }
  df <- data.frame(x = unname(x), y = 1)

  ggplot2::ggplot(df, ggplot2::aes(x = df$x, y = df$y, fill = df$x)) +
    ggplot2::geom_col() +
    ggplot2::coord_flip() +
    ggplot2::theme_void(base_size = 13) +
    ggplot2::ggtitle(palette) +
    ggplot2::theme(legend.position = "none",
                   plot.title.position =  "panel",
                   axis.text.y = ggplot2::element_text(),
                   plot.margin = ggplot2::unit(c(10, 10, 10, 10), "pt")) +
    ggplot2::scale_fill_manual(values = rev(df$x)) +
    ggplot2::scale_x_discrete(labels = rev(df$x)) +
    ggplot2::scale_y_continuous(expand = ggplot2::expansion(mult = 0.02))
}