plot(collgpa ~ hsgpa, data = Gpa)
mod <- lm(collgpa ~ hsgpa, data = Gpa)
abline(mod)               # add line
yhat <- predict(mod)      # fitted values
e <- resid(mod)           # residuals
cbind(Gpa, yhat, e)       # Table 2.1
cor(Gpa$hsgpa, Gpa$collgpa)
if (FALSE) {
library(ggplot2)
ggplot2::ggplot(data = Gpa, aes(x = hsgpa, y = collgpa)) + 
           geom_point() + 
           geom_smooth(method = "lm") + 
           theme_bw()
}
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