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How to add regression line equation and R2 on graph  

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Abhijith
(@abhijith)
Noble Member
Joined: 4 months ago
Posts: 1161
24/03/2021 11:39 am  

How to add regression line equation and R^2 on the ggplot. 

My code is as follows:

library(ggplot2)
df <- data.frame(x = c(1:100))
df$y <- 2 + 3 * df$x + rnorm(100, sd = 40)
p <- ggplot(data = df, aes(x = x, y = y)) +
            geom_smooth(method = "lm", se=FALSE, color="black", formula = y ~ x) +
            geom_point()
p

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Sathish Kumar
(@sathish)
Member Moderator
Joined: 4 months ago
Posts: 1203
24/03/2021 11:40 am  

Below is one solution:

# GET EQUATION AND R-SQUARED AS STRING
# SOURCE:  http://goo.gl/K4yh 

lm_eqn <- function(df){
    m <- lm(y ~ x, df);
    eq <- substitute(italic(y) == a + b %.% italic(x)*","~~italic(r)^2~"="~r2, 
         list(a = format(coef(m)[1], digits = 2), 
              b = format(coef(m)[2], digits = 2), 
             r2 = format(summary(m)$r.squared, digits = 3)))
    as.character(as.expression(eq));                 
}

p1 <- p + geom_text(x = 25, y = 300, label = lm_eqn(df), parse = TRUE)

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