|  | ## Loop Attributes

#### Synopsis

Iterates over the given features and applies the inner operators for each feature where the inner operators can access the current feature name by a macro.

#### Description

This operator takes an input data set and applies its inner operators as often as the number of features of the input data is. Inner operators can access the current feature name by a macro, whose name can be specified via the parameter `iteration_macro`.

The user can specify with a parameter if this loop should iterate over all features or only over features with a specific value type, i.e. only over numerical or over nominal features. A regular expression can also be specified which is used as a filter, i.e. the inner operators are only applied for feature names matching the filter expression.

#### Input

- example set: expects: ExampleSet

#### Output

- example set:

#### 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.
- iteration macro: The name of the macro which holds the name of the current feature in each iteration.

#### ExampleProcess