ggplot2 plotmath: using bquote to add (<=) sign in label error

July 3, 2023

I’m trying to add a less than or equal sign "<=" label in my ggplot but keep getting the error:

Error in grid.Call(C_textBounds, as.graphicsAnnot(x$label), x$x, x$y,  : 
  invalid mathematical annotation

Any suggestions on how I can fix this?

lower_limit <- 15

ggplot(mtcars, aes(wt, mpg)) + 
geom_point() + 
scale_y_continuous(limits = c(lower_limit, 35), 
breaks = c(lower_limit, 25, 35), 
labels = c(bquote(""<= .(lower_limit)), "25", "35"))

thank you in advance

>Solution :

You need to pass an expression vector as labels, and your code gives a list. Use as.expression() to convert it:

library(ggplot2)

lower_limit <- 15

ggplot(mtcars, aes(wt, mpg)) + 
  geom_point() + 
  scale_y_continuous(limits = c(lower_limit, 35), 
                     breaks = c(lower_limit, 25, 35), 
                     labels = as.expression(c(bquote("" <= .(lower_limit)), "25", "35")))
#> Warning: Removed 5 rows containing missing values (`geom_point()`).