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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:
- numeric:
This type of attribute represents a floating-point number.
- nominal:
This type of attribute represents a fixed set of nominal values.
- string:
This type of attribute represents a dynamically expanding set of
nominal values. String attributes are not used by the learning
schemes in Weka. They can be used, for example, to store an
identifier with each instance in a dataset.
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)
-
NOMINAL
- Constant set for nominal attributes.
-
NUMERIC
- Constant set for numeric attributes.
-
STRING
- Constant set for attributes with string values.
-
Attribute(String)
- Constructor for a numeric attribute.
-
Attribute(String, FastVector)
- Constructor for nominal attributes and string attributes.
-
addStringValue(String)
- Adds a string value to the list of valid strings for attributes
of type STRING and returns the index of the string.
-
copy()
- Produces a shallow copy of this attribute.
-
enumerateValues()
- Returns an enumeration of all the attribute's values if
the attribute is nominal or a string, null otherwise.
-
equals(Object)
- Tests if given attribute is equal to this attribute.
-
index()
- Returns the index of this attribute.
-
indexOfValue(String)
- Returns the index of a given attribute value.
-
isNominal()
- Test if the attribute is nominal.
-
isNumeric()
- Tests if the attribute is numeric.
-
isString()
- Tests if the attribute is a string.
-
main(String[])
- Simple main method for testing this class.
-
name()
- Returns the attribute's name.
-
numValues()
- Returns the number of attribute values.
-
toString()
- Returns a description of this attribute in ARFF format.
-
type()
- Returns the attribute's type as an integer.
-
value(int)
- Returns a value of a nominal or string attribute.
NUMERIC
public static final int NUMERIC
- Constant set for numeric attributes.
NOMINAL
public static final int NOMINAL
- Constant set for nominal attributes.
STRING
public static final int STRING
- Constant set for attributes with string values.
Attribute
public Attribute(String attributeName)
- Constructor for a numeric attribute.
- Parameters:
- attributeName - the name for the attribute
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.
copy
public Object copy()
- Produces a shallow copy of this attribute.
- Returns:
- a copy of this attribute with the same index
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
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
index
public final int index()
- Returns the index of this attribute.
- Returns:
- the index of this attribute
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
isNominal
public final boolean isNominal()
- Test if the attribute is nominal.
isNumeric
public final boolean isNumeric()
- Tests if the attribute is numeric.
isString
public final boolean isString()
- Tests if the attribute is a string.
name
public final String name()
- Returns the attribute's name.
- Returns:
- the attribute's name as a string
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
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
type
public final int type()
- Returns the attribute's type as an integer.
- Returns:
- s the attribute's type.
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
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
main
public static void main(String ops[])
- Simple main method for testing this class.
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