Modifying the decimal mark of stat_poly_eq

Question

I use the stat_poly_eq function from the ggpmisc package to add the regression equation in my ggplots. It works perfectly. However, I'd like to change the decimal mark of the equation from period to comma, and I can't figure out how to do this. Any suggestions?

data(mpg)

ggplot(mpg, aes(y = displ, x = hwy)) +
  geom_point(alpha = 0.5, color = "cadetblue") +
  geom_smooth(method = "lm", se = F, color = "black", size = 0.5) +
  stat_poly_eq(aes(label = paste(after_stat(eq.label),
                                 after_stat(rr.label),
                                 sep = "*plain(\",\")~~")),
               coef.digits = 3)

Answer 1

data(mpg)
library(ggpmisc)

my_formula <- y ~ x
myformat <- "y = %s %s x, R²: %s"

ggplot(mpg, aes(y = displ, x = hwy)) +
  geom_point(alpha = 0.5, color = "cadetblue") +
  geom_smooth(method = "lm", se = F, color = "black", size = 0.5) +
  stat_poly_eq(
    formula = my_formula, output.type = "numeric",
    mapping = aes(
      label = 
        sprintf(
          myformat,
          format(stat(coef.ls)[[1]][[1, "Estimate"]], digits = 3, decimal.mark = ","),
          format(stat(coef.ls)[[1]][[2, "Estimate"]], digits = 2, decimal.mark = ","),
          format(stat(r.squared), digits = 2, decimal.mark = ",")))
  ) 

I have elaborated my answer based on this post.

I hope this helps you! 😀