weka.core
Class DenseInstance

java.lang.Object
  weka.core.AbstractInstance
      weka.core.DenseInstance

All Implemented Interfaces:

Serializable, Copyable, Instance, RevisionHandler

public class DenseInstance
extends AbstractInstance

Class for handling an instance. All values (numeric, date, nominal, string or relational) are internally stored as floating-point numbers. If an attribute is nominal (or a string or relational), the stored value is the index of the corresponding nominal (or string or relational) 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 DenseInstance(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's attribute values are safe, ie. a change of an instance's attribute values 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: 9028 $

Author:

Eibe Frank ([email protected])

See Also:

Serialized Form

Field Summary

Fields inherited from class weka.core.AbstractInstance

s_numericAfterDecimalPoint

Constructor Summary

DenseInstance(double weight, double[] attValues)
Constructor that inititalizes instance variable with given values.

DenseInstance(Instance instance)
Constructor that copies the attribute values and the weight from the given instance.

DenseInstance(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

Object	copy() Produces a shallow copy of this instance.
String	getRevision() Returns the revision string.
int	index(int position) Returns the index of the attribute stored at the given position.
static void	main(String[] options) Main method for testing this class.
Instance	mergeInstance(Instance inst) Merges this instance with the given instance and returns the result.
int	numAttributes() Returns the number of attributes.
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	setValue(int attIndex, double value) Sets a specific value in the instance to the given value (internal floating-point format).
void	setValueSparse(int indexOfIndex, double value) Sets a specific value in the instance to the given value (internal floating-point format).
double[]	toDoubleArray() Returns the values of each attribute as an array of doubles.
String	toStringNoWeight() Returns the description of one instance (without weight appended).
String	toStringNoWeight(int afterDecimalPoint) Returns the description of one instance (without weight appended).
double	value(int attIndex) Returns an instance's attribute value in internal format.

Methods inherited from class weka.core.AbstractInstance

attribute, attributeSparse, classAttribute, classIndex, classIsMissing, classValue, dataset, deleteAttributeAt, enumerateAttributes, equalHeaders, equalHeadersMsg, hasMissingValue, insertAttributeAt, isMissing, isMissing, isMissingSparse, numClasses, relationalValue, relationalValue, setClassMissing, setClassValue, setClassValue, setDataset, setMissing, setMissing, setValue, setValue, setValue, setWeight, stringValue, stringValue, toString, toString, toString, toString, toString, toStringMaxDecimalDigits, value, valueSparse, weight

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

DenseInstance

public DenseInstance(Instance instance)

Constructor that copies the attribute values and the weight from the given instance. It does NOT perform a deep copy of the attribute values if the instance provided is also of type DenseInstance (it simply copies the reference to the array of values), otherwise it does. 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

DenseInstance

public DenseInstance(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

DenseInstance

public DenseInstance(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

Method Detail

copy

public 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 DenseInstance(instance)

Returns:

the shallow copy

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

mergeInstance

public Instance mergeInstance(Instance inst)

Merges this instance with the given instance and returns the result. Dataset is set to null. The returned instance is of the same type as this instance.

Parameters:

inst - the instance to be merged with this one

Returns:

the merged instances

numAttributes

public int numAttributes()

Returns the number of attributes.

Returns:

the number of attributes as an integer

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:

IllegalArgumentException - if numbers of attributes are unequal

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).

toDoubleArray

public double[] toDoubleArray()

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

Returns:

an array containing all the instance attribute values

toStringNoWeight

public String toStringNoWeight()

Returns the description of one instance (without weight appended). If the instance doesn't have access to a dataset, it returns the internal floating-point values. Quotes string values that contain whitespace characters. This method is used by getRandomNumberGenerator() in Instances.java in order to maintain backwards compatibility with weka 3.4.

Returns:

the instance's description as a string

toStringNoWeight

public String toStringNoWeight(int afterDecimalPoint)

Returns the description of one instance (without weight appended). If the instance doesn't have access to a dataset, it returns the internal floating-point values. Quotes string values that contain whitespace characters. This method is used by getRandomNumberGenerator() in Instances.java in order to maintain backwards compatibility with weka 3.4.

Parameters:

afterDecimalPoint - maximum number of digits after the decimal point for numeric values

Returns:

the instance'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).

main

public static void main(String[] options)

Main method for testing this class.

Parameters:

options - the commandline options - ignored

getRevision

public String getRevision()

Returns the revision string.

Specified by:

getRevision in interface RevisionHandler

Overrides:

getRevision in class AbstractInstance

Returns:

the revision