{ggtext} for images as x-axis labels

I’ve written a few times about using an image as an x-axis label, and the solutions have been slowly improving. This one blows all of them out of the water.

Claus Wilke (@ClausWilke) now has a {ggtext} package which can very neatly add images as x-axis labels!

This makes the solution as simple as

library(ggplot2)
library(ggtext)
library(rvest)

## GDP per capita, top 11 countries
url      <- "https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nominal)_per_capita"
html     <- xml2::read_html(url)
gdppc    <- html_table(html_nodes(html, "table")[3])[[1]][1:11,]

## clean up; remove non-ASCII and perform type conversions
gdppc$Country <- gsub("Â ", "", gdppc$Country)
gdppc$Country <- iconv(gdppc$Country, "latin1", "ASCII", sub="")
gdppc$Country[9] <- "United States of America"
gdppc$Rank    <- iconv(gdppc$Rank,    "latin1", "ASCII", sub="")
gdppc$`US$`   <- as.integer(sub(",", "", gdppc$`US$`))

## switching to a different source of flag images
labels <- setNames(
  paste0("<img src='http://www.senojflags.com/images/country-flag-icons/", 
         gsub(" ", "-", gdppc$Country), "-Flag.png'  width='30' /><br>", 
         sapply(strwrap(gdppc$Country, width = 10, simplify = FALSE), 
                function(x) paste(x, collapse = "<br>"))),
  gdppc$Country
)

## create a dummy dataset
npoints <- length(gdppc$Country)
y       <- gdppc$`US$`
x       <- gdppc$Country
dat     <- data.frame(x=factor(x, levels=gdppc$Country), y=y)

## NB: #85bb65 is the color of money in the USA apparently.
gg <- ggplot(dat, aes(x=x, y=y/1e3L, group=1)) 
gg <- gg + geom_bar(col="black", fill="#85bb65", stat="identity")
gg <- gg + scale_x_discrete(name = NULL, labels = labels)
gg <- gg + theme_minimal()
gg <- gg + scale_fill_discrete(guide=FALSE)
gg <- gg + theme(plot.background = element_rect(fill="grey90"))
gg <- gg + labs(title="GDP per capita", 
                subtitle="Top 11 countries", 
                x="", y="$US/1000", 
                caption=paste0("Source: ",url))
## ggtext::element_markdown
gg <- gg + theme(axis.text.x  = element_markdown(color = "black", size = 7), 
                 axis.text.y  = element_text(size=14),
                 axis.title.x = element_blank())
gg
{ggtext} makes this easy!

Figure 1: {ggtext} makes this easy!

This is an even nicer solution than I’ve been using, not only because it’s shorter to use, but also more flexible - markdown can be processed (using element_markdown) wherever element_text is used, such as axis text, legends, titles, etc…

I think this finally closes this chapter, but now it’s time to make some really cool graphs with images.


devtools::session_info()

## ─ Session info ──────────────────────────────────────────────────────────
##  setting  value                       
##  version  R version 3.5.2 (2018-12-20)
##  os       Pop!_OS 19.04               
##  system   x86_64, linux-gnu           
##  ui       X11                         
##  language en_AU:en                    
##  collate  en_AU.UTF-8                 
##  ctype    en_AU.UTF-8                 
##  tz       Australia/Adelaide          
##  date     2019-08-13                  
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##  source                              
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##  Github (rstudio/blogdown@be4e91c)   
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See also