Attribute Parameter Macro
(Custom Operators)
Synopsis
This operator can be used to define a macro which can be used by %{macro_name} in parameter values of succeeding operators of the current process. The value will be defined via an attribute selection parameter which is prefilled using the metadata. This is useful for process-defined custom operators.Description
This operator can be used to define a macro which can be used in parameter values of succeeding operators of the current process. Once the macro has been defined, the value of that macro can be used as parameter values in coming operators by writing the macro name in %{macro_name} format in the parameter value where 'macro_name' is the name of the macro specified when the macro was defined. The macro name is specified by the macro parameter and the macro value is an attribute name which can be selected from a dropdown filled by the metadata or typed in. The macro will be replaced in the value strings of parameters by the macro's value. This operator can also be used to re-define an existing macro.
The purpose of this operator is mainly to assist in creating process-defined custom operators. When selecting the value parameter of this operator for the custom operator, the custom operator will have an attribute dropdown prefilled by the metadata of the port to which the first input port of this operator is connected to.
This operator sets the value of a macro irrespective of any ExampleSet. That is why this operator can also exist on its own i.e. without being connected to any other operator. If you want to create a single macro from properties of a given input ExampleSet, the Extract Macro operator is the right operator.
Macros
A macro can be considered as a value that can be used by all operators of the current process that come after the macro has been defined. Whenever using macros, make sure that the operators are in the correct sequence. It is compulsory that the macro should be defined before it can be used in parameter values. The macro is one of the advanced topics of RapidMiner, please study the attached Example Process to develop a better understanding of macros. The Example Processes of the Extract Macro operator are also useful for understanding the concepts related to the macros.
There are also some predefined macros:
- %{process_name}: will be replaced by the name of the process (without path and extension)
- %{process_file}: will be replaced by the file name of the process (with extension)
- %{process_path}: will be replaced by the complete absolute path of the process file
- Several other short macros also exist, e.g. %{a} for the number of times the current operator was applied.
Please note that other operators like many of the loop operators (e.g. Loop Values , Loop Attributes) also add specific macros.
During the runtime the defined macros can be observed in the macro viewer.
Differentiation
Set Macro
The Attribute Parameter Macro operator is like the Set Macro operator with only one difference. The Set Macro operator can be used for setting arbitrary String values while in the Attribute Parameter Macro has as value an attribute name which can be selected from the metadata.
Input
through (Data table)This port should be connected to prefill the attribute selection dropdown. Any object connected at this port is delivered without any modifications to the output port. This operator can have multiple inputs. When one input is connected, another through input port becomes available which is ready to accept another input (if any). The order of inputs remains the same. The object supplied at the first through input port of this operator is available at the first through output port.
Output
- through (Data table)
Objects that were given as input are passed without changing to the output through this port. It is not compulsory to attach this port to any other port, the macro value is set even if this port is left without connections. This operator can have multiple outputs. When one output is connected, another through output port becomes available which is ready to deliver another output (if any). The order of outputs remains the same. The object delivered at the first through input port of this operator is delivered at the first through output port
Parameters
- macroThis parameter is used to specify the name of the macro. The macro can be accessed in succeeding operators of the current process by writing the macro's name in %{macro_name} format, where 'macro_name' is the name of the macro specified in this parameter.
- valueThis parameter is used to specify the value of the macro which should be an attribute name. Select one of the values prefilled from the metadata from the dropdown or type the name of an attribute. When the macro is accessed in succeeding operators of the current process by writing the macro's name in %{macro_name} format, it is replaced by the value of the macro specified by this parameter.
Tutorial Processes
Introduction to the Attribute Parameter Macro operator
This is a very basic process that demonstrates the use of the Attribute Parameter Macro operator. The process has two predefined inputs: At the first port is the Deals dataset and at the second input port the Golf dataset.
To start, consider the first input port: The Attribute Parameter Macro operator is used first of all. One macro is defined using the macro parameter and the value dropdown. The macro is named 'delete' and it is given the value 'Age' selected from the attribute dropdown. The 'delete' macro is then used in the Execute Script operator to delete that attribute. When you run the process you will see the Deals dataset with the Age attribute missing in the Results workspace.
Next, consider the second port: Again, the Attribute Parameter Macro operator is used first of all. Now, the macro is named 'attribute' and it is given the value 'Humidity' selected from the attribute dropdown. The 'attribute' macro is used in the Select Attributes operators for the attribute parameter inside the Branch operator. For a normal process we could directly select the 'Humidity' attribute in the dropdown of the attribute parameter of the Select Attribute operators. But when creating custom operators the heuristic to obtain the metadata is not always working when the operator is not directly connected to the root operator. When you run the process you will see an ExampleSet only containing of the Humidity attribute in the Results workspace.
This approach of using the Attribute Parameter Macro operator is mainly useful for creating custom operators. For creating a custom operator out of this process we would select the parameter 'value' of 'Attribute Parameter Macro' and call it 'delete attribute'. In the custom operator that would result in a parameter called 'delete attribute' with an attribute selection prefilled by the metadata of the first input port of the custom operator (since the first port is connected to the first input port of the Attribute Parameter Macro operator). Furthermore, we would select the parameter 'value' of 'Attribute Parameter Macro (2)' and call it 'select attribute'. That would result in a parameter called 'select attribute' with an attribute selection prefilled by the metadata of the second input port of the custom operator (since the second port is connected to the first input port of the Attribute Parameter Macro (2) operator).
