Partially italicize ggplot tick labels

partial_italic.R

library(tidyverse)

# Start with some dummy data
whale_data <- tribble(
  ~species,          ~prey,   ~order,
  "B. musculus",     "krill", 5,
  "B. physalus",     "fish",  3,
  "B. physalus",     "krill", 4,
  "M. novaeangliae", "fish",  1,
  "M. novaeangliae", "krill", 2
) %>% 
  mutate(a = runif(nrow(.)),
         b = a - runif(nrow(.)),
         c = a + runif(nrow(.))) %>% 
# Create a new column with the proper species/prey format
  mutate(tick_labels = fct_reorder(
    str_glue("italic(\"{species}\") ~ \"({prey})\""),
    order
  ))

# `labels = parse(text = ...` in scale_x_discrete() converts text to plotmath
ggplot(whale_data, aes(x = paste(species, prey), y = a)) +
  geom_pointrange(aes(ymin = b, ymax = c)) +
  scale_x_discrete(labels = parse(text = levels(whale_data$tick_labels))) +
  theme_minimal() +
  theme(axis.text.x = element_text(angle = 45, hjust = 1),
        axis.title.x = element_blank())