Extract Log Value (RapidMiner Studio Core)

Synopsis

This operator reads the specified value from the input ExampleSet and provides the value for logging.

Description

The Extract Log Value operator can be used for logging the value of the specified attribute at the specified index. The attribute name and index are specified through attribute name and example index parameters respectively. The values within an ExampleSet cannot be logged directly by the Log operator. The Extract Log Value operator makes the selected value loggable. This value can be logged by the Log operator. This value can be accessed in the Log operator at [Name of Extract Log Value operator][value][data_value]. Please study the attached Example Process for more information.

Logging and log-related operators store information into the log table. This information can be almost anything including parameter values of operators, apply-count of operators, execution time etc. The Log is mostly used when you want to see the values calculated during the execution of the process that are otherwise not visible. For example you want to see values of different parameters in all iterations of any Loop operator. For more information regarding logging please study the Log operator.

Input

  • example set (IOObject)

    This input port expects an ExampleSet. It is the output of the Retrieve operator in the attached Example Process. The output of other operators can also be used as input.

Output

  • example set (IOObject)

    The ExampleSet that was given as input is passed without changing to the output through this port. This is usually used to reuse the same ExampleSet in further operators or to view the ExampleSet in the Results Workspace.

Parameters

  • attribute_nameThis parameter specifies the name of the attribute whose value should be provided for logging. Range: string
  • example_indexThis parameter specifies the index of the example whose value should be provided for logging. Please note that negative indices are counted from the end of the data set. Positive counting starts with 1, negative counting starts with -1. Range: integer

Tutorial Processes

Logging the value of an attribute by Extract Log Value operator

The 'Golf' data set is loaded using the Retrieve operator. A breakpoint is inserted here so that you can have a look at the ExampleSet. You can see that the 'Outlook' attribute has value 'sunny' in the first example. This value will be logged by the coming operators. The Extract Log Value operator is applied to provide this value as a loggable value. Finally the Log operator is applied to store this value in the log table. Have a look at the log parameter settings in the Log operator. Only one column named 'Value' has been defined. Please note carefully how the attribute value has been accessed. Run the process and you will see one column with just a single entry in the Table View of the results of the Log operator. You can see that it stores the value of the 'Outlook' attribute from the first example.