Bubble chart with round country flag symbols in ggplot/ggimage - r

Question

I try to make a bubble chart with ggplot/ggimage by including the country flag. Here is a reproducible example:
library(dplyr)
library(ggplot)
library(ggimage)
A <- data.frame(X = c(1,4,5), Y = c(10, 1, 5), Z = c(1, 2, 3)/30, Country = c("FR", "BE", "IT"), CountryFlag = paste0("https://flagcdn.com/h20/", str_to_lower(Country), ".png"))
A_plot <- ggplot(A, mapping = aes(x = X, y = Y, size = I(Z), image = CountryFlag)) +
geom_image()
X11(); print(A_plot)
Except downloading the rounded flags, is that possible to transform the flag as rounded or is it possible to insert the country in a bubble. I tried the following code but it doesn't work:
library(dplyr)
library(ggplot)
library(ggimage)
A <- data.frame(X = c(1,4,5), Y = c(10, 1, 5), Z = c(1, 2, 3), Country = c("FR", "BE", "IT"), CountryFlag = paste0("https://flagcdn.com/h20/", str_to_lower(Country), ".png"))
A_plot <- ggplot(A, mapping = aes(x = X, y = Y, size = Z, image = CountryFlag)) +
geom_point(alpha = 0.5, col = "lightblue") +
geom_image()
X11(); print(A_plot)
I get the error:
Error in `[<-`(`*tmp*`, !is.na(alpha), 4, value = alpha[!is.na(alpha)]) :
(subscript) logical subscript too long
In addition: Warning message:
In rep(colour, length.out = length(alpha)) :
'x' is NULL so the result will be NULL
Any suggestion is welcome.

Answer 1

Here's a function that adds a circular mask to each flag. If we start with your plot,
A_plot
We get the urls and create some local filenames:
flags <- A_plot$data$CountryFlag
png_files <- sapply(strsplit(flags, "/"), function(x) x[length(x)])
Now we create some images with a circular mask and save them locally:
OK <- Map(function(flag, png) {
im <- magick::image_read(flag)
im <- magick::image_resize(im, magick::geometry_size_percent(500, 2000))
ii <- magick::image_info(im)
width <- ii$width
fig <- magick::image_draw(magick::image_blank(height, height))
symbols(width/2, width/2, circles=(width/2), bg='black', inches=FALSE, add=TRUE)
im2 <- magick::image_composite(im, fig, operator='copyopacity')
magick::image_write(im2, png)
}, flag = flags, png = png_files)
Now write these file paths as our image locations in the plot object:
A_plot$data$CountryFlag <- png_files
Which changes our plot to:
A_plot
For completeness, we should tidy up after ourselves once the plot is drawn:
sapply(png_files, unlink)

Answer 2

Funnily enough, someone just asked a question which pointed to a package for an easy way to get exactly what you want. The {ggflags} package (not on CRAN!) introduces geom_flag, which uses readily available round flag icons from the EmojiOne set as points.
library(tidyverse)
# devtools::install_github("jimjam-slam/ggflags")
library(ggflags)
Country <- c("FR", "BE", "IT")
A <- data.frame(
X = c(1, 4, 5), Y = c(10, 1, 5), Z = c(1, 2, 3), Country = tolower(Country))
ggplot(A, mapping = aes(x = X, y = Y, size = Z*3, country = Country)) +
geom_flag()+
# you can then set the scale as usual by using scale_size
scale_size_identity(guide = guide_legend())
Created on 2022-04-03 by the reprex package (v2.0.1)