Annotation and axis label tweaks in ggplot2

Optimising label placement in facetted graphs

Author

Affiliation

Cara Thompson

Building Stories with Data

Here’s a section of a faceted ggplot dataviz I’ve been working on today for an rfortherest client. Making use of a few handy scale_x_discrete() and theme() tweaks to make the labels line up nicely with the wider aesthetic.

Styling axis text on the fly with a custom function

On the x axis, the labels are "AREA<linebreak><Area number>", with the number using a larger font size than the word “area”. Here’s the relevant code snippet behind that:

# Simplified code
plot +
  facet_wrap(
    . ~ facetting_var,
    ncol = 1,
    scales = "free_y",
    strip.position = "left"
  )
scale_x_discrete(labels = function(x) {
  glue(
    "<span style='font-size:5pt'>
                           AREA<br></span>**{x}**"
  )
}) +
  theme(
    strip.background = element_rect(color = "orange", fill = "orange"),
    strip.text.y.left = element_text(color = "white", angle = 0, face = "bold"),
    axis.title.x = element_text(hjust = 0.4),
    axis.text.y = element_blank(),
    axis.text.x = ggtext::element_markdown(
      color = "gray",
      family = "Lato"
    ),
    panel.spacing = unit(0.75, "lines")
  )

Placing the x axis at the top of the graph

And here’s the other modification to help with readability: placing the x-axis at the top, so it reads more like a table.

This required me to modify axis.text.top.x inside theme() because axis.text.x no longer applied.

# Simplified relevant bits of code
plot +
  scale_x_discrete(
    expand = expansion(add = c(0.5, 2.5)),
    position = "top",
    labels = function(x) {
      glue::glue(
        "<span style='font-size:5pt'>{soil_type}<br></span>**{x}**"
      )
    }
  ) +
  theme(
    axis.text.x.top = ggtext::element_markdown(
      color = "gray",
      family = "Lato"
    )
  )

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