How to wrap an axis title that also has mathematical notation in ggplot2?-CodePudding

The title of my y-axis is long and includes mathematical notation at the end of it. Ideally, the title would occupy 2 rows with the top saying "Long Title Example" and the bottom saying "with Mathematical Operation (% yr-1)". How can I wrap the y-axis title?

I have seen this SO question but I can not seem to get it to work when there is mathematical notation in the title.

Example figure with a long title that includes mathematical notation

library(ggplot2)

ggplot(data = iris, aes(x = Sepal.Length, y = Sepal.Width))  
  geom_point(shape = 21, size = 4, aes(fill = factor(Species)))  
  stat_smooth(method = 'lm', se = F, color = "red")  
  ylab(expression(Long~Title~Example~with~Mathematical~Operation~("%"~yr^-1)))  
  xlab("Species")  
  labs(fill = "Species")  
  scale_y_continuous(breaks = seq(0,5,1), limits = c(0,5))  
  scale_x_continuous(breaks = seq(0,8,1), limits = c(0,8))  
  theme_bw()  
  theme(panel.grid = element_blank(),
        text = element_text(size = 18, color = "black"),
        axis.text.x = element_text(size = 18, color = "black"),
        axis.text.y = element_text(size = 18, color = 'black'),
        legend.title.align = 0.5,
        legend.position = c(0.15,0.2))

CodePudding user response：

Here is a potential solution:

library(ggplot2)

# x axis split over two lines
ggplot(data = iris, aes(x = Sepal.Length, y = Sepal.Width))  
  geom_point(shape = 21, size = 4, aes(fill = factor(Species)))  
  stat_smooth(method = 'lm', se = F, color = "red")  
  ylab(expression(atop(Long~Title~Example,
                       with~Mathematical~Operation~("%"~yr^"-1"))))  
  xlab("Species")  
  labs(fill = "Species")  
  scale_y_continuous(breaks = seq(0,5,1), limits = c(0,5))  
  scale_x_continuous(breaks = seq(0,8,1), limits = c(0,8))  
  theme_bw()  
  theme(panel.grid = element_blank(),
        text = element_text(size = 18, color = "black"),
        axis.text.x = element_text(size = 18, color = "black"),
        axis.text.y = element_text(size = 18, color = 'black'),
        legend.title.align = 0.5,
        legend.position = c(0.15,0.2))
#> `geom_smooth()` using formula 'y ~ x'

^{Created on 2022-03-14 by the reprex package (v2.0.1)}