Add p-value, R2 and equation to linear models in ggplot2

add_p_r2_eqn.R

library(ggplot2)

df <- data.frame(x = c(1:100))
df$y <- 2 + 3 * df$x + rnorm(100, sd = 40)
m <- lm(y ~ x, data = df)

summary(m)
# see that p <2e-16

# function to create the text equation
lm_eqn <- function(df, lm_object) {
  eq <-
    substitute(
      italic(y) == a + b %.% italic(x) * "," ~  ~ italic(r) ^ 2 ~ "=" ~ r2,
      list(
        a = format(coef(lm_object)[1], digits = 2),
        b = format(coef(lm_object)[2], digits = 2),
        r2 = format(summary(lm_object)$r.squared, digits = 3),
        p = p_value, digits = 2
        )
    )
  as.character(as.expression(eq))
}

# get the equation object in a format for use in ggplot2
eqn <- lm_eqn(df, m)

# plot everything
ggplot(data = df, aes(x = x, y = y)) +
  geom_smooth(method = "lm", formula = y ~ x) +
  geom_point() +
  annotate("text",
           x = 25,
           y = 300, 
           label = "italic(p) <2e-16",
           parse = TRUE) +
  annotate("text",
           x = 25,
           y = 315, 
           label = eqn,
           parse = TRUE) +
  theme_minimal()

## References ------------------------------------------------------------------
# https://stackoverflow.com/questions/7549694/adding-regression-line-equation-and-r2-on-graph
# https://groups.google.com/forum/#!topic/ggplot2/1TgH-kG5XMA
# https://stackoverflow.com/questions/5587676/pull-out-p-values-and-r-squared-from-a-linear-regression
# https://ggplot2.tidyverse.org/reference/annotate.html

gives this error
Error in lm_eqn(df, m) : object 'p_value' not found

The definition of lm_object is also missing.

Can you add this information?

Thanks in advance,
Norman