Inserting an image to a bar chart in ggplot

Question

I have three groups (a, b, c) with associated values, that I want to plot as bar chart.

Using ggplot, I would like to insert a different image (in png format) in each bar. So in bar a, I want to insert the image 'a.png', in bar b, the image 'b.png' and in c the image 'c.png'

df = data.frame(
  group = c('a', 'b', 'c'),
  value = 1:3)

ggplot(df, aes(group, value)) + 
  geom_col()

The few posts I found are not helpful or very old.

Inserting an image to ggplot outside the chart area

https://www.reddit.com/r/rstats/comments/6qh4kt/how_to_make_ggplot_not_beautiful_insert_pictures/

Do you have an idea?

Thanks

Answer 1

One option is to use ggimage. Source: https://guangchuangyu.github.io/pkgdocs/ggimage.html. Try this:

library(ggplot2)
library(ggimage)
library(dplyr)

set.seed(1234)

img <- list.files(system.file("extdata", package="ggimage"),
                  pattern="png", full.names=TRUE)

df = data.frame(
  group = c('a', 'b', 'c'),
  value = 1:3,
  image = sample(img, size=3, replace = TRUE)
) %>% 
  mutate(value1 = .5 * value)

ggplot(df, aes(group, value)) + 
  geom_col() + 
  geom_image(aes(image=image, y = value1), size=.2)

^{Created on 2020-03-19 by the reprex package (v0.3.0)}