[Humour] Pie chart pyramid

pie-chart-pyramid.R

## A paraphrase of http://flowingdata.com/2014/12/01/pie-chart-pyramid/
## See also https://github.com/lovrot/pie-chart-pyramid

library(ggplot2)
theme_set(theme_bw())

palette_part <- c(
    "Sky"="deepskyblue3",
    "Sunny side of pyramid"="yellow1",
    "Shady side of pyramid"="yellow3")

h <- 1.1

alpha_degrees <- 20  # between 0 and 90

alpha <- alpha_degrees/180*pi

x_1 <- cos(pi/4 - alpha)
x_2 <- sin(pi/4 - alpha)

beta <- c(atan(x_1/h), atan(x_2/h))

binoculars <- data.frame(
    part=factor(
        c("Sky", "Sunny side of pyramid",
            "Shady side of pyramid", "Sky"),
        levels=c("Sky", "Sunny side of pyramid",
            "Shady side of pyramid")),
    radians=c(pi - beta[1], beta[1] + beta[2],
        beta[1] - beta[2], pi - beta[1]))

gg <- ggplot(data=binoculars,
    aes(x=factor(1), y=radians, fill=part)) +
    geom_bar(width=1, stat="identity", position="fill") +
    scale_x_discrete(breaks=NULL, name="") +
    scale_y_continuous(breaks=NULL, name="") +
    scale_fill_manual(values=palette_part, name="") +
    theme(
        panel.grid.major.x=element_blank(),
        panel.border=element_blank()) +
    coord_polar(theta="y", direction=-1)

plot(gg)