practicalgg: Practical ggplot2

#' Composition of the 8th German Bundestag
#'
#' Composition of the 8th Bundestag, from 1976-1980. The `party` and `seat` columns should be self-explanatory.
#' The `colors_original` column holds the traditional colors used to represent these parties, and the `colors`
#' column holds variations of these colors that are less saturated.
#'
#' @references
#' Source: \url{https://en.wikipedia.org/wiki/Bundestag#Distribution_of_seats_in_the_Bundestag}
#'
#' @examples
#' library(tidyverse)
#' library(cowplot)
#' library(ggforce)
#'
#' # calculate the start and end angles for each pie
#' bund_pie <- bundestag %>%
#'   arrange(seats) %>%
#'   mutate(
#'     seat_total = sum(seats),
#'     end_angle = 2*pi*cumsum(seats)/seat_total,   # ending angle for each pie slice
#'     start_angle = lag(end_angle, default = 0),   # starting angle for each pie slice
#'     mid_angle = 0.5*(start_angle + end_angle),   # middle of each pie slice, for the text label
#'     hjust = ifelse(mid_angle>pi, 1, 0),
#'     vjust = ifelse(mid_angle<pi/2 | mid_angle>3*pi/2, 0, 1)
#'   )
#'
#' rpie <- 1
#' rlabel <- 1.05 * rpie
#'
#' ggplot(bund_pie) +
#'   geom_arc_bar(
#'     aes(
#'       x0 = 0, y0 = 0, r0 = 0, r = rpie,
#'       start = start_angle, end = end_angle, fill = colors
#'      )
#'   ) +
#'   geom_text(
#'     aes(
#'       x = rlabel*sin(mid_angle),
#'       y = rlabel*cos(mid_angle),
#'       label = party,
#'       hjust = hjust, vjust = vjust
#'     )
#'   ) +
#'   coord_fixed() +
#'   scale_x_continuous(limits = c(-1.6, 1.3), name = NULL, breaks = NULL, labels = NULL) +
#'   scale_y_continuous(limits = c(-1.1, 1.3), name = NULL, breaks = NULL, labels = NULL) +
#'   scale_fill_identity() +
#'   theme_map()
"bundestag"