Creating a half-donut, or parliamentary seating, chart

Question

I\'d like to create a chart displaying the size of the seats to a parliament, such as the one below, in ggplot2. My main problem is, essentially, how do I turn a donut chart to

Answer 1

FWIW, one might also check out the nice ggforce package:

library(tidyverse)
library(ggforce)
library(scales)
df %>%
  mutate_at(vars(starts_with("y")), rescale, to=pi*c(-.5,.5), from=0:1) %>%
  ggplot + 
  geom_arc_bar(aes(x0 = 0, y0 = 0, r0 = .5, r = 1, start = ymin, end = ymax, fill=Party)) + 
  coord_fixed()