|  | ## Work on Subset

#### Synopsis

Selects one attribute (or a subset) via a regular expression and applies its inner operators to the resulting subset.

#### Description

This operator can be used to select one attribute (or a subset) by defining a regular expression for the attribute name and applies its inner operators to the resulting subset. Please note that this operator will also use special attributes which makes it necessary for all preprocessing steps which should be performed on special attributes (and are normally not performed on special attributes).

This operator is also able to deliver the additional results of the inner operator if desired.

Afterwards, the remaining original attributes are added to the resulting example set if the parameter "keep_subset_only" is set to false (default).

Please note that this operator is very powerful and can be used to create new preprocessing schemes by combinating it with other preprocessing operators. Hoewever, there are two major restrictions (among some others): first, since the inner result will be combined with the rest of the input example set, the number of examples (data points) is not allowed to be changed inside of the subset preprocessing. Second, attribute role changes will not be delivered to the outside since internally all special attributes will be changed to regular for the inner operators and role changes can afterwards not be delivered.

#### Input

- example set: expects: ExampleSet

#### Output

- example set:
- through 1:

#### Parameters

- attribute filter type: The condition specifies which attributes are selected or affected by this operator.
- attribute: The attribute which should be chosen.
- attributes: The attribute which should be chosen.
- regular expression: A regular expression for the names of the attributes which should be kept.
- use except expression: If enabled, an exception to the specified regular expression might be specified. Attributes of matching this will be filtered out, although matching the first expression.
- except regular expression: A regular expression for the names of the attributes which should be filtered out although matching the above regular expression.
- value type: The value type of the attributes.
- use value type exception: If enabled, an exception to the specified value type might be specified. Attributes of this type will be filtered out, although matching the first specified type.
- except value type: Except this value type.
- block type: The block type of the attributes.
- use block type exception: If enabled, an exception to the specified block type might be specified.
- except block type: Except this block type.
- numeric condition: Parameter string for the condition, e.g. '>= 5'
- invert selection: Indicates if only attributes should be accepted which would normally filtered.
- include special attributes: Indicate if this operator should also be applied on the special attributes. Otherwise they are always kept.
- keep subset only: Indicates if the attributes which did not match the regular expression should be removed by this operator.
- deliver inner results: Indicates if the additional results (other than example set) of the inner operator should also be returned.

#### ExampleProcess