Skip to main content

Select Attributes

Synopsis

This Operator selects a subset of Attributes of an ExampleSet and removes the other Attributes.

Description

The Operator provides different filter types to make Attribute selection easy. Possibilities are for example: Direct selection of Attributes. Selection by a regular expression or selecting only Attributes without missing values. See parameterattribute filter typefor a detailed description of the different filter types.

Thetypeparameter can be used to decide whether to include or exclude the selected Attributes. Special Attributes (Attributes with Roles, like id, label, weight) are by default ignored in the selection. They will always remain in the resulting output ExampleSet. The parameteralso apply to special attributeschanges this.

Only the selected Attributes are delivered to the output port. The rest are removed from the ExampleSet.

Differentiation

Select by<...>Operators

There are several Operators that select Attributes according to their input. For example Select by Weights selects Attributes whose weights match a specified criterion. The Select by Random Operator selects a random subset of Attributes. Remove Attribute Range removes a range of Attributes according to the index of the Attributes. The Remove Useless Attributes Operator removes Attributes which can be considered to be useless according to some specified criteria. The Remove Correlated Attributes Operator removes Attributes which are correlated to each other.

Work on Subset

This Operator is a combination of the Select Attributes Operator and the Subprocess Operator. It applies the Operators in its inner process to an ExampleSet with only the Attributes which are selected by the attribute filter type. The inner result is merged back to the whole input ExampleSet.

Optimize Selection

This is an implementation of the forward selection feature selection method. It selects the most relevant Attributes according to a model which is trained inside the Operator. For details see the documentation of the Forward Selection Operator.

Optimize Selection

This is an implementation of the backward elimination feature selection method. It selects the most relevant Attributes according to an model which is trained inside the Operator. For details see the documentation of the Forward Selection Operator.

Filter Examples

This Operator does not select Attributes, but filters (or select) Examples. Thus, it does what Select Attributes does but applied to Examples instead of Attributes.

Input

example set

This input port expects an ExampleSet for which you want to select Attributes from.

Output

example set

The ExampleSet with only the selected Attributes is delivered to this output port.

original

The ExampleSet that was given as input is passed without changing to the output through this port.

Parameters

Type

This parameter can be used to decide whether to include or exclude the selected Attributes.include attributesist the default option. It configures the Operator to keep the selected Attributes and remove the remainder.exclude attributesleads to the inverse behaviour. It configures the Operator to remove the selected Attributes and keep the remainder. This also applies to special attributes if thealso apply to special attributesparameter is set to true.

Attribute filter type

This parameter allows you to select the Attribute selection filter; the method you want to use for selecting Attributes. It has the following options:

  • all attributes: This option selects all the Attributes of the ExampleSet, no Attributes are removed. This is the default option
  • one attribute: This option allows the selection of a single Attribute. The Attribute is selected by theselect attributeparameter.
  • a subset: This option allows the selection of multiple Attributes through a list (see parameterselect subset). If the meta data of the ExampleSet is known all Attributes are present in the list and the required ones can easily be selected.
  • regular expression: This option allows you to specify a regular expression for the Attribute selection. The regular expression filter is configured via the parametersexpressionandexclude expression.
  • type(s) of values:该选项允许属性的选择f particular type(s). The value type filter is configured via the parametertype of value.
  • no missing values: This option selects all Attributes of the ExampleSet which do not contain a missing value in any Example. Attributes that have even a single missing value are removed.

Select attribute

The required Attribute can be selected from this option. The Attribute name can be selected from the drop down box of the parameter if the meta data is known. Otherwise, the attribute name can be typed in manually.

Select subset

The required Attributes can be selected from this option. This opens a new window with two lists. All Attributes are present in the left list, if the meta data is known. They can be shifted to the right list, which is the list of selected Attributes that will make it to the output port. If the meta data is unknown, you can manually type in attribute names and use the green plus-button to add them to the list of selected attributes.

Expression

Attributes whose names match this expression will be selected. The expression can be specified through the button on the right that will open theEdit Regular Expressionmenu. This menu gives a good idea of regular expressions and it also allows you to try different expressions and preview the results simultaneously.

Exclude expression

这个选项允许您指定一个固定的表达sion. Attributes matching this expression will be filtered out even if they match the first expression (expression that was specified via theexpressionparameter).

Type of value

This option allows to select Attribute types. A subset of the following types can be chosen: real, integer, date-time, time, binominal, non-binominal.

Also apply to special attributes

Special Attributes are Attributes with roles (e.g. id, label..). By default all special Attributes are delivered to the output port regardless of the conditions in the Select Attributes Operator. If this parameter is set to true, special Attributes are also tested against the specified conditions and only those Attributes are selected that match the conditions.