Add regression line equation and R^2 on graph

📝 Title: How to Add Regression Line Equation and R^2 on a ggplot Graph

👋 Hey there! Are you struggling with adding a regression line equation and R^2 on a ggplot graph? Don't worry, I've got you covered! In this blog post, I'll walk you through a step-by-step guide to achieving this. 😊

✅ Problem: You want to visualize a regression line equation and R^2 on your ggplot graph but not sure how to do it.

⭐️ Solution: Follow these simple steps to add the regression line equation and R^2 on your graph:

1. First, make sure you have the ggplot2 library installed. If not, install it using the following code:

install.packages("ggplot2")
library(ggplot2)

1. Now, let's create some dummy data for our example. Run the following code to generate a dataset:

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

1. We'll use the geom_smooth() function with the "lm" method to add a regression line to our plot. Additionally, we need to set se = FALSE to remove the confidence interval. Include the formula = y ~ x argument to specify the regression equation. We'll also add color = "black" to set the line color. Finally, don't forget to include geom_point() to add the data points. Run the following code:

p <- ggplot(data = df, aes(x = x, y = y)) +
            geom_smooth(method = "lm", se = FALSE, color = "black", formula = y ~ x) +
            geom_point()

1. At this point, we have our basic graph. To add the regression line equation and R^2, we'll need to use the annotate() function. Add the following lines of code:

model <- lm(y ~ x, data = df)
eqn <- substitute(paste("Equation: ", y == a + b %.% x, ", R^2 = ", r2), 
                  list(a = format(coef(model)[1], digits = 2), 
                       b = format(coef(model)[2], digits = 2), 
                       r2 = format(summary(model)$r.squared, digits = 2)))

p + 
  annotate("text", x = max(df$x), y = max(df$y), label = as.character(as.expression(eqn)), 
           parse = TRUE, hjust = 1, vjust = 1, color = "red", fontface = "bold")

1. Finally, run the code, and you'll have your ggplot graph with the regression line equation and R^2 displayed on it. 🎉

📣 So there you have it! You can now easily add a regression line equation and R^2 on your ggplot graphs using these simple steps. Hope this guide was helpful in solving your problem! If you have any further questions or ideas, feel free to share them in the comments below. Happy coding! 😄💻