Learning

Learning a Bayesian Belief Network (BBN) means to learn the structure and parameters. The structure of a BBN is typically learned first, and then the parameters are learned afterwards. The signature of the the learn_structure(...) method is as follows.

learn_structure(df_path: str, meta_path: str, n_way=3,
                 ignore_neg_gt=-0.1, ignore_pos_lt=0.1,
                 n_regressions=10, solver='liblinear', penalty='l1', C=0.2,
                 robust_threshold=0.9) -> Dict[str, List[str]]

Since we are using logistic regression with LASSO regularization, you will need to specify how to accomplish the regression with some arguments. The solver can be either liblinear or saga. The penalty must be l1 and the regularization strength, C is a number between [0, 1]. For C, a smaller value means stronger regularlization. Please take a look at Scikit’s official documentation for additional information.

What is returned is a Python dictionary that stores the child to parent relationships. Here is an example of the dictionary that is returned.

1{
2 "e": ["d!b"],
3 "d": ["b!a"]
4}

After you have learned the child to parent relationships (or equivalently, parent to child relationships), you should then learn the parameters. The signature of the learn_parameters(...) function is as follows.

learn_parameters(df_path: str, pas: Dict[str, List[str]]) -> \
    Tuple[Dict[str, List[str]], nx.DiGraph, Dict[str, List[float]]]

The output of learn_parameters(...) is a tuple of 3 things.

  • domains of each variable

  • graphical structure

  • conditional probability tables for each variable

TODO

  • L00: Implement LASSO regression with continuous dependent variable.

  • L01: Implement LASSO regression with categorical independent variable.

  • L02: How do we implement LASSO regression with categorical dependent variable?

  • L03: How do we learn with partial ordering of the variables? (DONE)

  • L04: How do we learn with no ordering of the variables?

  • L05: Implement blacklisted or whitelisted edges.