Now let's do an example.
So here's your reminder of the formula and suppose this is my data.
I have four data points and for each data point I have three features,
the grade of the train, the bumpiness, whether there's a speed limit,
and then the speed that the car goes.
And i'm just making up some data here.
So let's start out at the top of the decision tree here.
So I have two slow examples and two fast examples.
Slow, slow, fast, fast.
So the first question is, what's the entropy of this node?
So let's do this piece by piece.
How many of the examples in this node are slow?
Write your answer here.