# Example to illustrate boosting
# T. Yee, 202305.



data(Boston, package = "MASS")


library("rpart")


# Set things up
n <- nrow(Boston)
Ngrid <- 500
range.crim <- with(Boston, range(crim))  # min and max
Newdata <- data.frame(crim = exp(seq(log(range.crim[1]),
                                     log(range.crim[2]),
                                     length = Ngrid)))



# Scatterplot
plot(medv ~ log(crim), Boston, las = 1, col = "blue",
     main = "Boosting regression tree example")



# Now do some boosting
library("gbm")
set.seed(1)
boost.boston <-
  gbm(medv ~ log(crim), data = Boston,
      distribution = "gaussian",
      n.trees = 747,  # Can control the complexity here
      interaction.depth = 1)  # Stump


Pred <- predict(boost.boston, Newdata)

# Add the boosted tree to the plot
lines(Pred ~ log(crim), Newdata, col = 1, lwd = 5)