DBMS_PREDICTIVE_ANALYTICS & Explain

There are 2 PL/SQL packages for performing data mining/predictive analytics in Oracle. The main PL/SQL package is DBMS_DATA_MINING. This package allows you to build data mining models and to apply them to new data. But there is another PL/SQL package.

The DBMS_PREDICTIVE_ANALYTICS package is very different to the DBMS_DATA_MINING package. The DBMS_PREDICTIVE_ANALYTICS package includes routines for predictive analytics, an automated form of data mining. With predictive analytics, you do not need to be aware of model building or scoring. All mining activities are handled internally by the predictive analytics procedure.

Predictive analytics routines prepare the data, build a model, score the model, and return the results of model scoring. Before exiting, they delete the model and supporting objects.

The package comes with the following functions: EXPLAIN, PREDICT and PROFILE. To get some of details about these functions we can run the following in SQL.

This blog post will look at the EXPLAIN function.

EXPLAIN creates an attribute importance model. Attribute importance uses the Minimum Description Length algorithm to determine the relative importance of attributes in predicting a target value. EXPLAIN returns a list of attributes ranked in relative order of their impact on the prediction. This information is derived from the model details for the attribute importance model.

Attribute importance models are not scored against new data. They simply return information (model details) about the data you provide.

I’ve written two previous blog posts on Attribute Importance. One of these was on how to calculate Attribute Importance using the Oracle Data Miner tool. In the ODM tool it is now called Feature Selection and is part of the Filter Columns node and the Attribute Importance model is not persisted in the database.  The second blog post was how you can create the Attribute Importance using the DBMS_DATA_MINING package.

EXPLAIN ranks attributes in order of influence in explaining a target column.

The syntax of the function is

DBMS_PREDICTIVE_ANALYTICS.EXPLAIN (
     data_table_name     IN VARCHAR2,
     explain_column_name IN VARCHAR2,
     result_table_name   IN VARCHAR2,
     data_schema_name    IN VARCHAR2 DEFAULT NULL);

where

data_table_name = Name of input table or view

explain_column_name = Name of column to be explained

result_table_name = Name of table where results are saved. It creates a new table in your schema.

data_schema_name = Name of schema where the input table or view resides. Default: the current schema.

So when calling the function you do not have to include the last parameter.

Using the same example what I have given in the previous blog posts (see about for the links to these) the following command can be run to generate the Attribute Importance.

BEGIN

    DBMS_PREDICTIVE_ANALYTICS.EXPLAIN(


        data_table_name      => 'mining_data_build_v',


        explain_column_name  => 'affinity_card',


        result_table_name    => 'PA_EXPLAIN');


END;

One thing that stands out is that it is a bit slower to run than the DBMS_DATA_MINING method. On my laptop it took approx. twice to three time longer to run. But in total it was less than a minute.

To display the results,

The results are ranked in a 0 to 1 range. Any attribute that had a negative value are set to zero.