|  | ## Nominal to Numerical

#### Synopsis

Maps all values to real values (usually simply using the internal indices).

#### Description

This operator maps all non numeric attributes to real valued attributes. Nothing is done for numeric attributes, binary attributes are mapped to 0 and 1. For nominal attributes one of the following calculations will be done:

- Dichotomization, i.e. one new attribute for each value of the nominal attribute. The new attribute which corresponds to the actual nominal value gets value 1 and all other attributes gets value 0.
- Alternatively the values of nominal attributes can be seen as equally ranked, therefore the nominal attribute will simply be turned into a real valued attribute, the old values results in equidistant real values.

At this moment the same applies for ordinal attributes, in a future release more appropriate values based on the ranking between the ordinal values may be included.

#### Input

- example set input: expects: ExampleSetMetaData: #examples: = 0; #attributes: 0

, Example set matching at least one selected attribute.

#### Output

- example set output:
- original:
- preprocessing model:

#### Parameters

- return preprocessing model: Indicates if the preprocessing model should also be returned
- create view: Create View to apply preprocessing instead of changing the data
- 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.

#### ExampleProcess