Select Subprocess (RapidMiner Studio Core)

Synopsis

This operator consists of multiple subprocesses but it executes only one subprocess at a time. This operator is similar to a switch, where numerous options exist but only one option is selected at a time. It is important to have a good understanding of subprocesses in order to use this operator effectively.

Description

It is very important to have a good understanding of the use of subprocesses in RapidMiner to understand this operator completely. A subprocess introduces a process within a process. Whenever a subprocess is reached during a process execution, first the entire subprocess is executed. Once the subprocess execution is complete, flow is returned to the process (the parent process). A subprocess can be considered as a small unit of a process, like in a process, all operators and combination of operators can be applied in a subprocess. That is why a subprocess can also be defined as a chain of operators that is subsequently applied. For more details about subprocesses please study the Subprocess operator.

Double-click on the Select Subprocess operator to go inside and view the subprocesses. The subprocesses are then shown in the same Process View. Here you can see the options to add or remove subprocesses. To go back to the parent process, click the blue-colored up arrow button in the Process View toolbar. This works like files and folders work in operating systems. Subprocesses can have subprocesses in them just like folders can have folders in them.

The Select Subprocess operator consists of multiple subprocesses but it executes only one subprocess at a time. The number of subprocesses can be easily controlled. You can easily add or remove subprocesses. The process to be executed is selected by the select which parameter. Macros can be provided in the select which parameter. Thus the subprocess to be executed can be controlled by using macros. If this operator is placed in any Loop operator this operator will be executed multiple number of times. The true power of this operator comes into play when it is used with other operators like various Macro and Loop operators. For example, if this operator is placed in any Loop operator and the select which parameter is controlled by a macro then this operator can be used to dynamically change the process setup. This might be useful in order to test different layouts, e.g. the gain by using different preprocessing steps or the quality of a certain learner.

Input

input
The Select Subprocess operator can have multiple inputs. When one input is connected, another 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 input port of the Select Subprocess operator is available at the first input port of the nested chain (inside the subprocess).Don't forget to connect all inputs in correct order. Make sure that you have connected the right number of ports at all levels of the chain.

Output

output
The Select Subprocess operator can have multiple outputs. When one output is connected, another 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 output port of subprocess is delivered at the first output of the Select Subprocess operator. Don't forget to connect all outputs in correct order. Make sure that you have connected the right number of ports at all levels of the chain.

Parameters

select_whichThis parameter indicates which subprocess should be applied. True power of this operator comes into play when the select which parameter is specified through a macro. Range: integer

Tutorial Processes

Applying different classification operators on Golf data set using the Select Subprocess operator

The 'Golf' data set is loaded using the Retrieve operator. The Select Subprocess operator is applied on it. Double-click on the Select Subprocess operator to see the subprocesses in it. As you can see, there are four subprocesses:

Subprocess 1: The k-NN operator is applied on the input and the resulting model is passed to the output. Subprocess 2: The Naive Bayes operator is applied on the input and the resulting model is passed to the output. Subprocess 3: The Decision Tree operator is applied on the input and the resulting model is passed to the output. Subprocess 4: The input is directly connected to the output.

Only one of these subprocesses can be executed at a time. The subprocess to be executed can be controlled by the select which parameter. The select which parameter is set to 1, thus the first subprocess will be executed. When you run the process you will see the model created by the k-NN operator in the Results workspace. To execute the second subprocess set the select which parameter to 2 and run the process again. You will see the model generated by the Naive Bayes operator in the Results Workspace. To execute the third subprocess set the select which parameter to 3 and run the process again. You will see the model generated by the Decision Tree operator in the Results Workspace. To execute the fourth subprocess set the select which parameter to 4 and run the process again. Now you will see the 'Golf' data set in the Results Workspace because no operator was applied in the fourth subprocess.