|  | ## Select Attributes

#### Synopsis

This operator allowes to select which attributes should be part of the resulting

#### Description

This operator selects which attributes of an ExampleSet should be kept and which are removed. Therefore, different filter types may be selected in the parameter attribute filter type and only attributes fulfilling this condition type are selected. The rest will be removed from the ExampleSet. There's a global switch to invert the outcome, so that all attributes which would have been originally discarded will be kept and vice versa. To invert the decision, use the invert selection parameter.

These types are available

- all: Will simply select each attribute
- single: This will allow you to select a single attribute name. It might be selected from the drop down box of parameter attribute if the meta data is known
- subset: Let's you choose a number of attributes from a list. This will not work if no meta data is present. Each known attribute is shown in the list and might be selected.
- regular_expression: This let's you specify a regular expression. Each attribute whose name matches this expression will be selected. Regular expressions are a very powerful tool but need a detailed explanation to beginners. Please refer to one of the several tutorials available on the internet for a more detailed description.
- value_type: Select only attributes of a certain type. Please mention that the types are hierarchical: For example are binominal attributes nomina as well as polynominal.
- block_type: Similar to value_type this let's you select the attributes depending on their block type.
- no_missing_values: Will select all attributes which don't contain a missing value in any example.
- numeric_value_filter: This will select the attributes by testing if all their values of all examples match this condition or if they aren't not numerical. The numeric condition might be specified by typing a numerical condition. For example the parameter string "> 6" will keep all nominal attributes and all numeric attributes having a value of greater 6 in every example. A combination of conditions is possible: "> 6 && < 11" or "<= 5 || < 0". But && and || must not be mixed.

#### Input

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

#### Output

- example set output:
- original:

#### 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.

#### ExampleProcess