How to Create a Scatterplot with a Regression Line in R


Often when we perform simple linear regression, we’re interested in creating a scatterplot to visualize the various combinations of x and y values.

Fortunately, R makes it easy to create scatterplots using the plot() function. For example:

#create some fake data
data <- data.frame(x = c(1, 1, 2, 3, 4, 4, 5, 6, 7, 7, 8, 9, 10, 11, 11),
                   y = c(13, 14, 17, 12, 23, 24, 25, 25, 24, 28, 32, 33, 35, 40, 41))

#create scatterplot of data
plot(data$x, data$y)

Scatterplot in R

It’s also easy to add a regression line to the scatterplot using the abline() function. For example:

#fit a simple linear regression model
model <- lm(y ~ x, data = data)

#add the fitted regression line to the scatterplot
abline(model)

Scatterplot with regression line in R

We can also add confidence interval lines to the plot by using the predict() function. For example:

#define range of x values
newx = seq(min(data$x),max(data$x),by = 1)

#find 95% confidence interval for the range of x values 
conf_interval <- predict(model, newdata=data.frame(x=newx), interval="confidence",
                         level = 0.95)

#create scatterplot of values with regression line 
plot(data$x, data$y)
abline(model)

#add dashed lines (lty=2) for the 95% confidence interval
lines(newx, conf_interval[,2], col="blue", lty=2)
lines(newx, conf_interval[,3], col="blue", lty=2)

Regression line with confidence interval in R

Or we could instead add prediction interval lines to the plot by specifying the interval type within the predict() function. For example:

#define range of x values
newx = seq(min(data$x),max(data$x),by = 1)

#find 95% prediction interval for the range of x values 
pred_interval <- predict(model, newdata=data.frame(x=newx), interval="prediction",
                         level = 0.95)

#create scatterplot of values with regression line 
plot(data$x, data$y)
abline(model)

#add dashed lines (lty=2) for the 95% confidence interval
lines(newx, pred_interval[,2], col="red", lty=2)
lines(newx, pred_interval[,3], col="red", lty=2)

Regression line with prediction interval lines in R

Lastly, we can make the plot more aesthetically pleasing by adding a title, changing the axes names, and changing the shape of the individual points in the plot.

plot(data$x, data$y,
     main = "Scatterplot of x vs. y", #add title
     pch=16, #specify points to be filled in
     xlab='x', #change x-axis name
     ylab='y') #change y-axis name

abline(model, col='steelblue') #specify color of regression line

Regression line with scatterplot in R

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