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Class weka.core.Attribute

java.lang.Object
   |
   +----weka.core.Attribute

public class Attribute
extends Object
implements Copyable, Serializable
Class for handling an attribute. Once an attribute has been created, it can't be changed.

Three attribute types are supported:

Typical usage (code from the main() method of this class):

...
// Create numeric attributes "length" and "weight"
Attribute length = new Attribute("length");
Attribute weight = new Attribute("weight");

// Create vector to hold nominal values "first", "second", "third"
FastVector my_nominal_values = new FastVector(3);
my_nominal_values.addElement("first");
my_nominal_values.addElement("second");
my_nominal_values.addElement("third");

// Create nominal attribute "position"
Attribute position = new Attribute("position", my_nominal_values);
...

Version:
$Revision: 1.8 $
Author:
Eibe Frank (eibe@cs.waikato.ac.nz)

Variable Index

 o NOMINAL
Constant set for nominal attributes.
 o NUMERIC
Constant set for numeric attributes.
 o STRING
Constant set for attributes with string values.

Constructor Index

 o Attribute(String)
Constructor for a numeric attribute.
 o Attribute(String, FastVector)
Constructor for nominal attributes and string attributes.

Method Index

 o addStringValue(String)
Adds a string value to the list of valid strings for attributes of type STRING and returns the index of the string.
 o copy()
Produces a shallow copy of this attribute.
 o enumerateValues()
Returns an enumeration of all the attribute's values if the attribute is nominal or a string, null otherwise.
 o equals(Object)
Tests if given attribute is equal to this attribute.
 o index()
Returns the index of this attribute.
 o indexOfValue(String)
Returns the index of a given attribute value.
 o isNominal()
Test if the attribute is nominal.
 o isNumeric()
Tests if the attribute is numeric.
 o isString()
Tests if the attribute is a string.
 o main(String[])
Simple main method for testing this class.
 o name()
Returns the attribute's name.
 o numValues()
Returns the number of attribute values.
 o toString()
Returns a description of this attribute in ARFF format.
 o type()
Returns the attribute's type as an integer.
 o value(int)
Returns a value of a nominal or string attribute.

Variables

 o NUMERIC
 public static final int NUMERIC
Constant set for numeric attributes.

 o NOMINAL
 public static final int NOMINAL
Constant set for nominal attributes.

 o STRING
 public static final int STRING
Constant set for attributes with string values.

Constructors

 o Attribute
 public Attribute(String attributeName)
Constructor for a numeric attribute.

Parameters:
attributeName - the name for the attribute
 o Attribute
 public Attribute(String attributeName,
                  FastVector attributeValues)
Constructor for nominal attributes and string attributes. If a null vector of attribute values is passed to the method, the attribute is assumed to be a string.

Parameters:
attributeName - the name for the attribute
attributeValues - a vector of strings denoting the attribute values. Null if the attribute is a string attribute.

Methods

 o copy
 public Object copy()
Produces a shallow copy of this attribute.

Returns:
a copy of this attribute with the same index
 o enumerateValues
 public final Enumeration enumerateValues()
Returns an enumeration of all the attribute's values if the attribute is nominal or a string, null otherwise.

Returns:
enumeration of all the attribute's values
 o equals
 public final boolean equals(Object other)
Tests if given attribute is equal to this attribute.

Parameters:
other - the Object to be compared to this attribute
Returns:
true if the given attribute is equal to this attribute
Overrides:
equals in class Object
 o index
 public final int index()
Returns the index of this attribute.

Returns:
the index of this attribute
 o indexOfValue
 public final int indexOfValue(String value)
Returns the index of a given attribute value. (The index of the first occurence of this value.)

Parameters:
value - the value for which the index is to be returned
Returns:
the index of the given attribute value if attribute is nominal or a string, -1 if it is numeric or the value can't be found
 o isNominal
 public final boolean isNominal()
Test if the attribute is nominal.

 o isNumeric
 public final boolean isNumeric()
Tests if the attribute is numeric.

 o isString
 public final boolean isString()
Tests if the attribute is a string.

 o name
 public final String name()
Returns the attribute's name.

Returns:
the attribute's name as a string
 o numValues
 public final int numValues()
Returns the number of attribute values. Returns 0 for numeric attributes and string attributes.

Returns:
the number of attribute values
 o toString
 public final String toString()
Returns a description of this attribute in ARFF format. Quotes strings if they contain whitespace characters, or if they are a question mark.

Returns:
a description of this attribute as a string
Overrides:
toString in class Object
 o type
 public final int type()
Returns the attribute's type as an integer.

Returns:
s the attribute's type.
 o value
 public final String value(int valIndex)
Returns a value of a nominal or string attribute. Returns an empty string if the attribute is neither nominal nor a string attribute.

Parameters:
valIndex - the value's index
Returns:
the attribute's value as a string
 o addStringValue
 public int addStringValue(String value)
Adds a string value to the list of valid strings for attributes of type STRING and returns the index of the string. The string will not be added if already present.

Parameters:
value - The string value to add
Returns:
the index assigned to the string, or -1 if the attribute is not of type Attribute.STRING
 o main
 public static void main(String ops[])
Simple main method for testing this class.


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