6.034 Artificial Intelligence - Recitations, fall 2004 online slides on learning

Next: Top-Down Induction of Decision Previous: Inducing Decision Trees

Decision Tree Learning

  • Any concept that can be expressed as a propositional statement can be expressed using a decision tree

  • No type of representation is efficient for all kinds of functions
    How represent $m$ of $n$?

  • Once we know how to use a decision tree, the next question is, how do we automatically construct a decision tree?

  • One possibility: search through the space of all possible decision trees
    All possible $n$ features at root
    For each root, $n-1$ possible features at each child
    $\cdots$

    Keep the hypotheses that are consistent with training examples
    Among these, keep one that satisfies bias

  • Too slow!

  • Another possibility: construct one path for each positive example
    Not very general

  • Another possibility: find smallest decision tree consistent with all examples
    Inductive Bias: Occam's Razor