weka.core
Class Instance

java.lang.Object
  weka.core.Instance

All Implemented Interfaces:

Copyable, java.io.Serializable

Direct Known Subclasses:

IndividualInstance, SparseInstance

public class Instance

extends java.lang.Object

implements Copyable, java.io.Serializable

Class for handling an instance. All values (numeric, nominal, or string) are internally stored as floating-point numbers. If an attribute is nominal (or a string), the stored value is the index of the corresponding nominal (or string) value in the attribute's definition. We have chosen this approach in favor of a more elegant object-oriented approach because it is much faster.

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

...
// Create empty instance with three attribute values
Instance inst = new Instance(3);

// Set instance's values for the attributes "length", "weight", and "position"
inst.setValue(length, 5.3);
inst.setValue(weight, 300);
inst.setValue(position, "first");

// Set instance's dataset to be the dataset "race"
inst.setDataset(race);

// Print the instance
System.out.println("The instance: " + inst);
...


All methods that change an instance are safe, ie. a change of an instance does not affect any other instances. All methods that change an instance's attribute values clone the attribute value vector before it is changed. If your application heavily modifies instance values, it may be faster to create a new instance from scratch.

Version:

$Revision: 1.15 $

Author:

Eibe Frank (eibe@cs.waikato.ac.nz)

See Also:

Serialized Form

Field Summary

protected double[]	m_AttValues The instance's attribute values.
protected Instances	m_Dataset The dataset the instance has access to.
protected double	m_Weight The instance's weight.
protected static double	MISSING_VALUE Constant representing a missing value.

Constructor Summary

protected	Instance() Private constructor for subclasses.
	Instance(double weight, double[] attValues) Constructor that inititalizes instance variable with given values.
	Instance(Instance instance) Constructor that copies the attribute values and the weight from the given instance.
	Instance(int numAttributes) Constructor of an instance that sets weight to one, all values to be missing, and the reference to the dataset to null.

Method Summary

Attribute	attribute(int index) Returns the attribute with the given index.
Attribute	attributeSparse(int indexOfIndex) Returns the attribute with the given index.
Attribute	classAttribute() Returns class attribute.
int	classIndex() Returns the class attribute's index.
boolean	classIsMissing() Tests if an instance's class is missing.
double	classValue() Returns an instance's class value in internal format.
java.lang.Object	copy() Produces a shallow copy of this instance.
Instances	dataset() Returns the dataset this instance has access to.
void	deleteAttributeAt(int position) Deletes an attribute at the given position (0 to numAttributes() - 1).
java.util.Enumeration	enumerateAttributes() Returns an enumeration of all the attributes.
boolean	equalHeaders(Instance inst) Tests if the headers of two instances are equivalent.
(package private) void	forceDeleteAttributeAt(int position) Deletes an attribute at the given position (0 to numAttributes() - 1).
(package private) void	forceInsertAttributeAt(int position) Inserts an attribute at the given position (0 to numAttributes()) and sets its value to be missing.
private void	freshAttributeVector() Clones the attribute vector of the instance and overwrites it with the clone.
int	index(int position) Returns the index of the attribute stored at the given position.
void	insertAttributeAt(int position) Inserts an attribute at the given position (0 to numAttributes()).
boolean	isMissing(Attribute att) Tests if a specific value is "missing".
boolean	isMissing(int attIndex) Tests if a specific value is "missing".
boolean	isMissingSparse(int indexOfIndex) Tests if a specific value is "missing".
static boolean	isMissingValue(double val) Tests if the given value codes "missing".
static void	main(java.lang.String[] options) Main method for testing this class.
Instance	mergeInstance(Instance inst) Merges this instance with the given instance and returns the result.
static double	missingValue() Returns the double that codes "missing".
int	numAttributes() Returns the number of attributes.
int	numClasses() Returns the number of class labels.
int	numValues() Returns the number of values present.
void	replaceMissingValues(double[] array) Replaces all missing values in the instance with the values contained in the given array.
void	setClassMissing() Sets the class value of an instance to be "missing".
void	setClassValue(double value) Sets the class value of an instance to the given value (internal floating-point format).
void	setClassValue(java.lang.String value) Sets the class value of an instance to the given value.
void	setDataset(Instances instances) Sets the reference to the dataset.
void	setMissing(Attribute att) Sets a specific value to be "missing".
void	setMissing(int attIndex) Sets a specific value to be "missing".
void	setValue(Attribute att, double value) Sets a specific value in the instance to the given value (internal floating-point format).
void	setValue(Attribute att, java.lang.String value) Sets a value of an nominal or string attribute to the given value.
void	setValue(int attIndex, double value) Sets a specific value in the instance to the given value (internal floating-point format).
void	setValue(int attIndex, java.lang.String value) Sets a value of a nominal or string attribute to the given value.
void	setValueSparse(int indexOfIndex, double value) Sets a specific value in the instance to the given value (internal floating-point format).
void	setWeight(double weight) Sets the weight of an instance.
java.lang.String	stringValue(Attribute att) Returns the string value of a nominal, string, or date attribute for the instance.
java.lang.String	stringValue(int attIndex) Returns the string value of a nominal, string, or date attribute for the instance.
double[]	toDoubleArray() Returns the values of each attribute as an array of doubles.
java.lang.String	toString() Returns the description of one instance.
java.lang.String	toString(Attribute att) Returns the description of one value of the instance as a string.
java.lang.String	toString(int attIndex) Returns the description of one value of the instance as a string.
double	value(Attribute att) Returns an instance's attribute value in internal format.
double	value(int attIndex) Returns an instance's attribute value in internal format.
double	valueSparse(int indexOfIndex) Returns an instance's attribute value in internal format.
double	weight() Returns the instance's weight.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

MISSING_VALUE

protected static final double MISSING_VALUE

Constant representing a missing value.

See Also:

Constant Field Values

m_Dataset

protected Instances m_Dataset

The dataset the instance has access to. Null if the instance doesn't have access to any dataset. Only if an instance has access to a dataset, it knows about the actual attribute types.

m_AttValues

protected double[] m_AttValues

The instance's attribute values.

m_Weight

protected double m_Weight

The instance's weight.

Constructor Detail

Instance

public Instance(Instance instance)

Constructor that copies the attribute values and the weight from the given instance. Reference to the dataset is set to null. (ie. the instance doesn't have access to information about the attribute types)

Parameters:

instance - the instance from which the attribute values and the weight are to be copied

Instance

public Instance(double weight,
                double[] attValues)

Constructor that inititalizes instance variable with given values. Reference to the dataset is set to null. (ie. the instance doesn't have access to information about the attribute types)

Parameters:

weight - the instance's weight

attValues - a vector of attribute values

Instance

public Instance(int numAttributes)

Constructor of an instance that sets weight to one, all values to be missing, and the reference to the dataset to null. (ie. the instance doesn't have access to information about the attribute types)

Parameters:

numAttributes - the size of the instance

Instance

protected Instance()

Private constructor for subclasses. Does nothing.

Method Detail

attribute

public Attribute attribute(int index)

Returns the attribute with the given index.

Parameters:

index - the attribute's index

Returns:

the attribute at the given position

Throws:

UnassignedDatasetException - if instance doesn't have access to a dataset

attributeSparse

public Attribute attributeSparse(int indexOfIndex)

Returns the attribute with the given index. Does the same thing as attribute().

Parameters:

indexOfIndex - the index of the attribute's index

Returns:

the attribute at the given position

Throws:

UnassignedDatasetException - if instance doesn't have access to a dataset

classAttribute

public Attribute classAttribute()

Returns class attribute.

Returns:

the class attribute

Throws:

UnassignedDatasetException - if the class is not set or the instance doesn't have access to a dataset

classIndex

public int classIndex()

Returns the class attribute's index.

Returns:

the class index as an integer

Throws:

UnassignedDatasetException - if instance doesn't have access to a dataset

classIsMissing

public boolean classIsMissing()

Tests if an instance's class is missing.

Returns:

true if the instance's class is missing

Throws:

UnassignedClassException - if the class is not set or the instance doesn't have access to a dataset

classValue

public double classValue()

Returns an instance's class value in internal format. (ie. as a floating-point number)

Returns:

the corresponding value as a double (If the corresponding attribute is nominal (or a string) then it returns the value's index as a double).

Throws:

UnassignedClassException - if the class is not set or the instance doesn't have access to a dataset

copy

public java.lang.Object copy()

Produces a shallow copy of this instance. The copy has access to the same dataset. (if you want to make a copy that doesn't have access to the dataset, use new Instance(instance)

Specified by:

copy in interface Copyable

Returns:

the shallow copy

dataset

public Instances dataset()

Returns the dataset this instance has access to. (ie. obtains information about attribute types from) Null if the instance doesn't have access to a dataset.

Returns:

the dataset the instance has accesss to

deleteAttributeAt

public void deleteAttributeAt(int position)

Deletes an attribute at the given position (0 to numAttributes() - 1). Only succeeds if the instance does not have access to any dataset because otherwise inconsistencies could be introduced.

Throws:

java.lang.RuntimeException - if the instance has access to a dataset

enumerateAttributes

public java.util.Enumeration enumerateAttributes()

Returns an enumeration of all the attributes.

Returns:

enumeration of all the attributes

Throws:

UnassignedDatasetException - if the instance doesn't have access to a dataset

equalHeaders

public boolean equalHeaders(Instance inst)

Tests if the headers of two instances are equivalent.

Returns:

true if the header of the given instance is equivalent to this instance's header

Throws:

UnassignedDatasetException - if instance doesn't have access to any dataset

index

public int index(int position)

Returns the index of the attribute stored at the given position. Just returns the given value.

Parameters:

position - the position

Returns:

the index of the attribute stored at the given position

insertAttributeAt

public void insertAttributeAt(int position)

Inserts an attribute at the given position (0 to numAttributes()). Only succeeds if the instance does not have access to any dataset because otherwise inconsistencies could be introduced.

Throws:

java.lang.RuntimeException - if the instance has accesss to a dataset

java.lang.IllegalArgumentException - if the position is out of range

isMissing

public boolean isMissing(int attIndex)

Tests if a specific value is "missing".

Parameters:

attIndex - the attribute's index

isMissingSparse

public boolean isMissingSparse(int indexOfIndex)

Tests if a specific value is "missing". Does the same thing as isMissing() if applied to an Instance.

Parameters:

indexOfIndex - the index of the attribute's index

isMissing

public boolean isMissing(Attribute att)

Tests if a specific value is "missing". The given attribute has to belong to a dataset.

Parameters:

att - the attribute

isMissingValue

public static boolean isMissingValue(double val)

Tests if the given value codes "missing".

Parameters:

val - the value to be tested

Returns:

true if val codes "missing"

mergeInstance

public Instance mergeInstance(Instance inst)

Merges this instance with the given instance and returns the result. Dataset is set to null.

Parameters:

inst - the instance to be merged with this one

Returns:

the merged instances

missingValue

public static double missingValue()

Returns the double that codes "missing".

Returns:

the double that codes "missing"

numAttributes

public int numAttributes()

Returns the number of attributes.

Returns:

the number of attributes as an integer

numClasses

public int numClasses()

Returns the number of class labels.

Returns:

the number of class labels as an integer if the class attribute is nominal, 1 otherwise.

Throws:

UnassignedDatasetException - if instance doesn't have access to any dataset

numValues

public int numValues()

Returns the number of values present. Always the same as numAttributes().

Returns:

the number of values

replaceMissingValues

public void replaceMissingValues(double[] array)

Replaces all missing values in the instance with the values contained in the given array. A deep copy of the vector of attribute values is performed before the values are replaced.

Parameters:

array - containing the means and modes

Throws:

java.lang.IllegalArgumentException - if numbers of attributes are unequal

setClassMissing

public void setClassMissing()

Sets the class value of an instance to be "missing". A deep copy of the vector of attribute values is performed before the value is set to be missing.

Throws:

UnassignedClassException - if the class is not set

UnassignedDatasetException - if the instance doesn't have access to a dataset

setClassValue

public void setClassValue(double value)

Sets the class value of an instance to the given value (internal floating-point format). A deep copy of the vector of attribute values is performed before the value is set.

Parameters:

value - the new attribute value (If the corresponding attribute is nominal (or a string) then this is the new value's index as a double).

Throws:

UnassignedClassException - if the class is not set

UnaddignedDatasetException - if the instance doesn't have access to a dataset

setClassValue

public final void setClassValue(java.lang.String value)

Sets the class value of an instance to the given value. A deep copy of the vector of attribute values is performed before the value is set.

Parameters:

value - the new class value (If the class is a string attribute and the value can't be found, the value is added to the attribute).

Throws:

UnassignedClassException - if the class is not set

UnassignedDatasetException - if the dataset is not set

java.lang.IllegalArgumentException - if the attribute is not nominal or a string, or the value couldn't be found for a nominal attribute

setDataset

public final void setDataset(Instances instances)

Sets the reference to the dataset. Does not check if the instance is compatible with the dataset. Note: the dataset does not know about this instance. If the structure of the dataset's header gets changed, this instance will not be adjusted automatically.

Parameters:

instances - the reference to the dataset

setMissing

public final void setMissing(int attIndex)

Sets a specific value to be "missing". Performs a deep copy of the vector of attribute values before the value is set to be missing.

Parameters:

attIndex - the attribute's index

setMissing

public final void setMissing(Attribute att)

Sets a specific value to be "missing". Performs a deep copy of the vector of attribute values before the value is set to be missing. The given attribute has to belong to a dataset.

Parameters:

att - the attribute

setValue

public void setValue(int attIndex,
                     double value)

Sets a specific value in the instance to the given value (internal floating-point format). Performs a deep copy of the vector of attribute values before the value is set.

Parameters:

attIndex - the attribute's index

value - the new attribute value (If the corresponding attribute is nominal (or a string) then this is the new value's index as a double).

setValueSparse

public void setValueSparse(int indexOfIndex,
                           double value)

Sets a specific value in the instance to the given value (internal floating-point format). Performs a deep copy of the vector of attribute values before the value is set. Does exactly the same thing as setValue().

Parameters:

indexOfIndex - the index of the attribute's index

value - the new attribute value (If the corresponding attribute is nominal (or a string) then this is the new value's index as a double).

setValue

public final void setValue(int attIndex,
                           java.lang.String value)

Sets a value of a nominal or string attribute to the given value. Performs a deep copy of the vector of attribute values before the value is set.

Parameters:

attIndex - the attribute's index

value - the new attribute value (If the attribute is a string attribute and the value can't be found, the value is added to the attribute).

Throws:

UnassignedDatasetException - if the dataset is not set

java.lang.IllegalArgumentException - if the selected attribute is not nominal or a string, or the supplied value couldn't be found for a nominal attribute

setValue

public final void setValue(Attribute att,
                           double value)

Sets a specific value in the instance to the given value (internal floating-point format). Performs a deep copy of the vector of attribute values before the value is set, so if you are planning on calling setValue many times it may be faster to create a new instance using toDoubleArray. The given attribute has to belong to a dataset.

Parameters:

att - the attribute

value - the new attribute value (If the corresponding attribute is nominal (or a string) then this is the new value's index as a double).

setValue

public final void setValue(Attribute att,
                           java.lang.String value)

Sets a value of an nominal or string attribute to the given value. Performs a deep copy of the vector of attribute values before the value is set, so if you are planning on calling setValue many times it may be faster to create a new instance using toDoubleArray. The given attribute has to belong to a dataset.

Parameters:

att - the attribute

value - the new attribute value (If the attribute is a string attribute and the value can't be found, the value is added to the attribute).

Throws:

java.lang.IllegalArgumentException - if the the attribute is not nominal or a string, or the value couldn't be found for a nominal attribute

setWeight

public final void setWeight(double weight)

Sets the weight of an instance.

Parameters:

weight - the weight

stringValue

public final java.lang.String stringValue(int attIndex)

Returns the string value of a nominal, string, or date attribute for the instance.

Parameters:

attIndex - the attribute's index

Returns:

the value as a string

Throws:

java.lang.IllegalArgumentException - if the attribute is not a nominal, string, or date attribute.

UnassignedDatasetException - if the instance doesn't belong to a dataset.

stringValue

public final java.lang.String stringValue(Attribute att)

Returns the string value of a nominal, string, or date attribute for the instance.

Parameters:

att - the attribute

Returns:

the value as a string

Throws:

java.lang.IllegalArgumentException - if the attribute is not a nominal, string, or date attribute.

UnassignedDatasetException - if the instance doesn't belong to a dataset.

toDoubleArray

public double[] toDoubleArray()

Returns the values of each attribute as an array of doubles.

Returns:

an array containing all the instance attribute values

toString

public java.lang.String toString()

Returns the description of one instance. If the instance doesn't have access to a dataset, it returns the internal floating-point values. Quotes string values that contain whitespace characters.

Returns:

the instance's description as a string

toString

public final java.lang.String toString(int attIndex)

Returns the description of one value of the instance as a string. If the instance doesn't have access to a dataset, it returns the internal floating-point value. Quotes string values that contain whitespace characters, or if they are a question mark.

Parameters:

attIndex - the attribute's index

Returns:

the value's description as a string

toString

public final java.lang.String toString(Attribute att)

Returns the description of one value of the instance as a string. If the instance doesn't have access to a dataset it returns the internal floating-point value. Quotes string values that contain whitespace characters, or if they are a question mark. The given attribute has to belong to a dataset.

Parameters:

att - the attribute

Returns:

the value's description as a string

value

public double value(int attIndex)

Returns an instance's attribute value in internal format.

Parameters:

attIndex - the attribute's index

Returns:

the specified value as a double (If the corresponding attribute is nominal (or a string) then it returns the value's index as a double).

valueSparse

public double valueSparse(int indexOfIndex)

Returns an instance's attribute value in internal format. Does exactly the same thing as value() if applied to an Instance.

Parameters:

indexOfIndex - the index of the attribute's index

Returns:

the specified value as a double (If the corresponding attribute is nominal (or a string) then it returns the value's index as a double).

value

public double value(Attribute att)

Returns an instance's attribute value in internal format. The given attribute has to belong to a dataset.

Parameters:

att - the attribute

Returns:

the specified value as a double (If the corresponding attribute is nominal (or a string) then it returns the value's index as a double).

weight

public final double weight()

Returns the instance's weight.

Returns:

the instance's weight as a double

forceDeleteAttributeAt

void forceDeleteAttributeAt(int position)

Deletes an attribute at the given position (0 to numAttributes() - 1).

forceInsertAttributeAt

void forceInsertAttributeAt(int position)

Inserts an attribute at the given position (0 to numAttributes()) and sets its value to be missing.

freshAttributeVector

private void freshAttributeVector()

Clones the attribute vector of the instance and overwrites it with the clone.

main

public static void main(java.lang.String[] options)

Main method for testing this class.