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Data Dictionaries

A data dictionary is the metadata that describes features of a data set. The NumericTableFeature and DataSourceFeature structures describe a particular feature within a dictionary of the associated numeric table and data source respectively. These structures specify:

  • Whether the feature is continuous, categorical, or ordinal

  • Underlying data types (double, integer, and so on) used to represent feature values

The DataSourceFeature structure also specifies:

  • Possible values for a categorical feature

  • The feature name

The DataSourceDictionary class is a data dictionary that describes raw data associated with the corresponding data source. The NumericTableDictionary class is a data dictionary that describes in-memory numeric data associated with the corresponding numeric table. Both classes provide generic methods for dictionary manipulation, such as accessing a particular data feature, setting and retrieving the number of features, and adding a new feature. Respective DataSource and NumericTable classes have generic dictionary manipulation methods, such as getDictionary() and setDictionary().

To create a dictionary from the data source context, you can do one of the following:

  • Set the doDictionaryFromContext flag in the DataSource constructor.

  • Call to the createDictionaryFromContext() method.