|  | ## Replace Missing Values

#### Synopsis

Replaces missing values in examples.

#### Description

Replaces missing values in examples. If a value is missing, it is replaced by one of the functions "minimum", "maximum", "average", and "none", which is applied to the non missing attribute values of the example set. "none" means, that the value is not replaced. The function can be selected using the parameter list `columns`. If an attribute's name appears in this list as a key, the value is used as the function name. If the attribute's name is not in the list, the function specified by the `default` parameter is used. For nominal attributes the mode is used for the average, i.e. the nominal value which occurs most often in the data. For nominal attributes and replacement type zero the first nominal value defined for this attribute is used. The replenishment "value" indicates that the user defined parameter should be used for the replacement.

#### 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.
- default: Function to apply to all columns that are not explicitly specified by parameter 'columns'.
- columns: List of replacement functions for each column.
- replenishment value: This value is used for some of the replenishment types.

#### ExampleProcess