There's not much more to ask than what I've written in the title.
Some of the values I want to predict are outside of the range used to build the regression model.
You can use the
predict function. Try:
set.seed(123) x <- 1:10 y <- -2 + 3 * x + rnorm(10) our_data <- data.frame(y = y, x = x) our_model <- lm(y ~ x, data = our_data) predict(our_model, newdata = data.frame(x = 20))
Once your model and its parameters are fixed, there's only one way to do it: plug in the covariate values of the point you want to extrapolate at.