File 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 a file path that can be selected with a file chooser. 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 the file path in the value parameter. 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 process can use the chosen file path from the macro.
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 File 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 the File Parameter Macro operator can use a file chooser to set the value.
Input
through (Data table)It is not compulsory to connect any object with this port. 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
- file endingsThis parameter is used to specify file endings for the file chooser of the value parameter. A list of file endings can be specified. File endings should not have a leading dot. If no file endings are specified, all files are allowed by default.
- 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 file path value of the macro. Use the file chooser to select the file. 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 File Parameter Macro operator
This is a very basic process that demonstrates the use of the File Parameter Macro operator. The File Parameter Macro operator is used first of all. One macro is defined using the macro parameter and the value parameter which can be defined with the file chooser. The allowed file endings are set to 'xml' only so that the file chooser allows to select xml files. The macro is named 'file' and it is given the selected xml file value. Note that this operator is not connected to any other operator; it can exist at its own. Always make sure that the macro is defined before it is used in the parameter values.
Afterwards, the selected file is opened with the Open File operator by using the macro in the filename parameter and supplied to a subprocess that can handle only xml files.
This approach of using the File Parameter Macro operator together with File operators like Open File, Rename File or Move File or operators from the Text extension is mainly useful for custom operators. For creating a custom operator out of this process we would select the parameter 'value' of 'File Parameter Macro' and call it 'xml file'. The file chooser of the file parameter in the custom operator would then by default show only xml files in contrast to when we just expose the filename parameter of the Open File operator.
