R package ggpmisc: Putting hat on y in Regression Equation

Question

I'm using R package ggpmisc. Wonder how to put hat on y in Regression Equation or how to get custom Response and Explanatory variable name in Regression Equation on graph.

library(ggplot2)
library(ggpmisc)

df <- data.frame(x1 = c(1:100))
set.seed(12345)
df$y1 <- 2 + 3 * df$x1 + rnorm(100, sd = 40)

p <- ggplot(data = df, aes(x = x1, y = y1)) +
  geom_smooth(method = "lm", se=FALSE, color="black", formula = y ~ x) +
  stat_poly_eq(formula = y ~ x, 
               aes(label = paste(..eq.label.., ..rr.label.., sep = "~~~")), 
               parse = TRUE) +         
  geom_point()
p

Answer 1

I would turn off the default value for y that is pasted in and build your own formula. For example

ggplot(data = df, aes(x = x1, y = y1)) +
  geom_smooth(method = "lm", se=FALSE, color="black", formula = y ~ x) +
  stat_poly_eq(formula = y ~ x, eq.with.lhs=FALSE,
      aes(label = paste("hat(italic(y))","~`=`~",..eq.label..,"~~~", ..rr.label.., sep = "")), 
      parse = TRUE) +         
  geom_point()

We use eq.with.lhs=FALSE to turn off the automatic inclusion of y= and then we paste() the hat(y) on to the front (with the equals sign). Note that the formatting comes from the ?plotmath help page.