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# Set Minus (RapidMiner Studio Core)

## Synopsis

This operator returns those examples of the ExampleSet (given at the*example set input*port) whose IDs are not contained within the other ExampleSet (given at the

*subtrahend*port). It is necessary that both ExampleSets should have the ID attribute. The ID attribute of both ExampleSets should be of the same type.

## Description

This operator performs a set minus on two ExampleSets on the basis of the ID attribute i.e. the resulting ExampleSet contains all the examples of the minuend ExampleSet (given at the *example set input* port) whose IDs do not appear in the subtrahend ExampleSet (given at the *subtrahend* port). It is important to note that the ExampleSets do not need to have the same number of columns or the same data types. The operation only depends on the ID attributes of the ExampleSets. It should be made sure that the ID attributes of both ExampleSets are of the same type i.e. either both are nominal or both are numerical.

## Differentiation

### Intersect

The Set Minus and Intersect operators can be considered as opposite of each other. The Intersect operator performs a set intersect on two ExampleSets on the basis of the ID attribute i.e. the resulting ExampleSet contains all the examples of the first ExampleSet whose IDs appear in the second ExampleSet.## Input

- example set input (IOObject)
This input port expects an ExampleSet. It is the output of the Generate ID operator in the attached Example Process because this operator only works if the ExampleSets have the ID attribute.

- subtrahend (IOObject)
This input port expects an ExampleSet. It is the output of the Generate ID operator in the attached Example Process because this operator only works if the ExampleSets have the ID attribute.

## Output

- example set output (IOObject)
The ExampleSet with remaining examples (i.e. examples remaining after the set minus) of the minuend ExampleSet is output of this port.

- original (IOObject)
The ExampleSet that was given as input (at example set input port) 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.

## Tutorial Processes

### Introduction to the Set Minus operator

The 'Golf' data set is loaded using the Retrieve operator. The Generate ID operator is applied on it with the offset parameter set to 0. Thus the ids of the 'Golf' data set are from 1 to 14. A breakpoint is inserted here so you can have a look at the 'Golf' data set. The 'Polynomial' data set is loaded using the Retrieve operator. The Generate ID operator is applied on it with the offset parameter set to 10. Thus the ids of the 'Polynomial' data set are from 11 to 210. A breakpoint is inserted here so you can have a look at the 'Polynomial' data set.

The Set Minus operator is applied next. The 'Golf' data set is provided at the example set input port and the 'Polynomial' data set is provided at the subtrahend port. The order of ExampleSets is very important. The Set Minus operator compares the ids of the 'Golf' data set with the ids of the 'Polynomial' data set and then returns only those examples of the 'Golf' data set whose id is not present in the 'Polynomial' data set. The 'Golf' data set ids are from 1 to 14 and the 'Polynomial' data set ids are from 11 to 210. Thus 'Golf' data set examples with ids 1 to 10 are returned by the Set Minus operator. It is important to note that the meta data of both ExampleSets is very different but it does not matter because the Set Minus operator only depends on the ID attribute.

If the ExampleSets are switched at the input ports of the Set Minus operator the results will be very different. In this case the Set Minus operator returns only those examples of the 'Polynomial' data set whose id is not present in the 'Golf' data set. The 'Golf' data set ids are from 1 to 14 and the 'Polynomial' data set ids are from 11 to 210. Thus the 'Polynomial' data set examples with ids 15 to 210 are returned by the Set Minus operator.