I am trying to learn decision trees but it has been difficult because the examples are extremely long and tedious and everybody seems to have a different algorithm in mind
After some digging I found a reliable set of notes online. However, I have the following two questions
What algorithm is this?
What is the meaning of $\mathbb{I}$?
It would be great if anyone can clarify this.
Here are the notes: http://www.stats.ox.ac.uk/~flaxman/HT17_lecture13.pdf