ggplot, sf package, How make simple pie graph on map

Question

I would like to make pie graph with ggplot and sf package. I have very simple data and un think there is simple method to do. All my data are pourcent :

data <- data.frame(Territory = c(1, 2, 3, 4, 5), 
                      Pins = c(25, 45, 45, 60, 75),
                      oak = c(45, 50, 45, 20, 15), 
                      land = c(30, 5, 10, 20, 10), 
                      sum = c(100, 100, 100, 100, 100))

And my graph code :

read_sf("territories.shp") %>%
  left_join(data, by = "Territory") %>%
  ggplot() +
  geom_sf(aes(fill = Pins), color = "black") + theme_bw() +
  xlab("") + ylab("") +
  scale_fill_distiller(palette = "Spectral") +
  geom_sf_text(aes(label = Territory), colour = "coral4", size = 4) 

In my shapefile I have information about n° of territory, so I didn't need to put longitude and latitude information. When I used geom_sf_text, labels are placed in the center of each sub-part of map, and and this is where I would like to put my pies.

Do you know a simple method to help me please?

thanks !

Answer 1

I don't know how much shorter this code is than the answers in the thread you linked but it at least uses the sf package. Here is one alternative using the cowplot package. I treated the pie charts like inset plots following: https://www.r-spatial.org/r/2018/10/25/ggplot2-sf-3.html

library(sf)
library(tidyr)
library(dplyr)
library(ggplot2)
library(cowplot)


states        <- sf::st_as_sf(maps::map("state", plot = FALSE, fill = TRUE))
state_coords <- st_coordinates(st_centroid(states)) %>%
  data.frame(stringsAsFactors = FALSE) %>%
  mutate(ID = states$ID) %>%
  mutate(X = (abs(abs(X) - abs(st_bbox(states)$xmin)) /
      as.numeric(abs(st_bbox(states)$xmin) - abs(st_bbox(states)$xmax))) - 0.5,
        Y = abs(abs(abs(Y) - abs(st_bbox(states)$ymin)) /
         as.numeric(abs(st_bbox(states)$ymin) - abs(st_bbox(states)$ymax))
        ))

dt     <- data.frame(Territory = c(1, 2, 3, 4, 5),
                   ID = c("california", "wyoming", "new york",
                          "kansas", "georgia"),
                   pins = c(25, 45, 45, 60, 75),
                   oak = c(45, 50, 45, 20, 15),
                   land = c(30, 5, 10, 20, 10))
res <- tidyr::gather(dt, key = "key", value = "value", -Territory, -ID) %>%
  left_join(state_coords)

make_pie <- function(dt, title = NA, legend.position = 0){
  if(is.na(title)){
    title <- unique(dt$ID)
  }
  ggplot() +
    geom_bar(data = dt,
             aes(x = "", y = value, fill = key),
             stat = "identity", width = 1) +
    coord_polar("y") +
    theme_void() +
    theme(legend.position = legend.position) +
    ggtitle(title)
}

terr1 <- make_pie(dplyr::filter(res, Territory == 1))
terr2 <- make_pie(dplyr::filter(res, Territory == 2))
terr3 <- make_pie(dplyr::filter(res, Territory == 3))
terr4 <- make_pie(dplyr::filter(res, Territory == 4))
terr5 <- make_pie(dplyr::filter(res, Territory == 5))

(gg_states <- ggplot(data = states) +
  geom_sf() +
    scale_x_continuous(expand = c(0, 0)) +
    scale_y_continuous(expand = c(0, 0 )) +
  theme(legend.position = 0,
        plot.margin = unit(c(0,0,0,0), "cm"))
    )

leg <- get_legend(make_pie(res, "", legend.position = "left"))

draw_plot_loc <- function(plot, dt){
  draw_plot(plot, x = dt$X[1], y = dt$Y[1],
            height = 0.2)
}

(all <-
ggdraw(gg_states) +
  draw_plot_loc(terr1, dplyr::filter(res, Territory == 1)) +
  draw_plot_loc(terr2, dplyr::filter(res, Territory == 2)) +
  draw_plot_loc(terr3, dplyr::filter(res, Territory == 3)) +
  draw_plot_loc(terr4, dplyr::filter(res, Territory == 4)) +
  draw_plot_loc(terr5, dplyr::filter(res, Territory == 5))
  )

cowplot::plot_grid(all, leg, rel_widths = c(1, 0.1))

I got most of the way there brute forcing the calculation between geographic coordinates and the draw_plot 0-1 grid but it's not perfect.