instance.java

wekaUT是 university texas austin 开发的基于weka的半指导学习(semi supervised learning)的分类器

/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 *    Instance.java
 *    Copyright (C) 1999 Eibe Frank
 *
 */

package weka.core;

import java.util.*;
import java.io.*;

/**
 * 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. <p>
 *
 * Typical usage (code from the main() method of this class): <p>
 *
 * <code>
 * ... <br>
 *      
 * // Create empty instance with three attribute values <br>
 * Instance inst = new Instance(3); <br><br>
 *     
 * // Set instance's values for the attributes "length", "weight", and "position"<br>
 * inst.setValue(length, 5.3); <br>
 * inst.setValue(weight, 300); <br>
 * inst.setValue(position, "first"); <br><br>
 *   
 * // Set instance's dataset to be the dataset "race" <br>
 * inst.setDataset(race); <br><br>
 *   
 * // Print the instance <br>
 * System.out.println("The instance: " + inst); <br>
 *
 * ... <br>
 * </code><p>
 *
 * 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.
 *
 * @author Eibe Frank ([e-mail])
 * @version $Revision: 1.1.1.1 $ 
 */
public class Instance implements Copyable, Serializable {
  
  /** Constant representing a missing value. */
  protected static final double MISSING_VALUE = Double.NaN;

  /** 
   * 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.  
   */
  protected Instances m_Dataset;

  /** The instance's attribute values. */
  protected double[] m_AttValues;

  /** The instance's weight. */
  protected double m_Weight;

  /**
   * 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)
   *
   * @param instance the instance from which the attribute
   * values and the weight are to be copied 
   */
  public Instance(Instance instance) {
    
    m_AttValues = instance.m_AttValues;
    m_Weight = instance.m_Weight;
    m_Dataset = null;
  }

  /**
   * 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)
   *
   * @param weight the instance's weight
   * @param attValues a vector of attribute values 
   */
  public Instance(double weight, double[] attValues){
    
    m_AttValues = attValues;
    m_Weight = weight;
    m_Dataset = null;
  }

  /**
   * 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)
   *
   * @param numAttributes the size of the instance 
   */
  public Instance(int numAttributes) {
    
    m_AttValues = new double[numAttributes];
    for (int i = 0; i < m_AttValues.length; i++) {
      m_AttValues[i] = MISSING_VALUE;
    }
    m_Weight = 1;
    m_Dataset = null;
  }

  /**
   * Returns the attribute with the given index.
   *
   * @param index the attribute's index
   * @return the attribute at the given position
   * @exception UnassignedDatasetException if instance doesn't have access to a
   * dataset
   */ 
  public Attribute attribute(int index) {
   
    if (m_Dataset == null) {
      throw new UnassignedDatasetException("Instance doesn't have access to a dataset!");
    }
    return m_Dataset.attribute(index);
  }

  /**
   * Returns the attribute with the given index. Does the same
   * thing as attribute().
   *
   * @param indexOfIndex the index of the attribute's index 
   * @return the attribute at the given position
   * @exception UnassignedDatasetException if instance doesn't have access to a
   * dataset
   */ 
  public Attribute attributeSparse(int indexOfIndex) {
   
    if (m_Dataset == null) {
      throw new UnassignedDatasetException("Instance doesn't have access to a dataset!");
    }
    return m_Dataset.attribute(indexOfIndex);
  }

  /**
   * Returns class attribute.
   *
   * @return the class attribute
   * @exception UnassignedDatasetException if the class is not set or the
   * instance doesn't have access to a dataset
   */
  public Attribute classAttribute() {

    if (m_Dataset == null) {
      throw new UnassignedDatasetException("Instance doesn't have access to a dataset!");
    }
    return m_Dataset.classAttribute();
  }

  /**
   * Returns the class attribute's index.
   *
   * @return the class index as an integer 
   * @exception UnassignedDatasetException if instance doesn't have access to a dataset 
   */
  public int classIndex() {
    
    if (m_Dataset == null) {
      throw new UnassignedDatasetException("Instance doesn't have access to a dataset!");
    }
    return m_Dataset.classIndex();
  }

  /**
   * Tests if an instance's class is missing.
   *
   * @return true if the instance's class is missing
   * @exception UnassignedClassException if the class is not set or the instance doesn't
   * have access to a dataset
   */
  public boolean classIsMissing() {

    if (classIndex() < 0) {
      throw new UnassignedClassException("Class is not set!");
    }
    return isMissing(classIndex());
  }

  /**
   * Returns an instance's class value in internal format. (ie. as a
   * floating-point number)
   *
   * @return 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).
   * @exception UnassignedClassException if the class is not set or the instance doesn't
   * have access to a dataset 
   */
  public double classValue() {
    
    if (classIndex() < 0) {
      throw new UnassignedClassException("Class is not set!");
    }
    return value(classIndex());
  }

  /**
   * 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 
   * <code>new Instance(instance)</code>
   *
   * @return the shallow copy
   */
  public Object copy() {

    Instance result = new Instance(this);
    result.m_Dataset = m_Dataset;
    return result;
  }

  /**
   * 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.
   *
   * @return the dataset the instance has accesss to
   */
  public Instances dataset() {

    return m_Dataset;
  }

  /**
   * 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.
   *
   * @param pos the attribute's position
   * @exception RuntimeException if the instance has access to a
   * dataset 
   */
  public void deleteAttributeAt(int position) {

    if (m_Dataset != null) {
      throw new RuntimeException("Instance has access to a dataset!");
    }
    forceDeleteAttributeAt(position);
  }

  /**
   * Returns an enumeration of all the attributes.
   *
   * @return enumeration of all the attributes
   * @exception UnassignedDatasetException if the instance doesn't
   * have access to a dataset 
   */
  public Enumeration enumerateAttributes() {

    if (m_Dataset == null) {
      throw new UnassignedDatasetException("Instance doesn't have access to a dataset!");
    }
    return m_Dataset.enumerateAttributes();
  }

  /**
   * Tests if the headers of two instances are equivalent.
   *
   * @param instance another instance
   * @return true if the header of the given instance is 
   * equivalent to this instance's header
   * @exception UnassignedDatasetException if instance doesn't have access to any
   * dataset
   */
  public boolean equalHeaders(Instance inst) {

    if (m_Dataset == null) {
      throw new UnassignedDatasetException("Instance doesn't have access to a dataset!");
    }
    return m_Dataset.equalHeaders(inst.m_Dataset);
  }

  /**
   * Returns the index of the attribute stored at the given position.
   * Just returns the given value.
   *
   * @param position the position 
   * @return the index of the attribute stored at the given position
   */
  public int index(int position) {

    return 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.
   *
   * @param pos the attribute's position
   * @exception RuntimeException if the instance has accesss to a
   * dataset
   * @exception IllegalArgumentException if the position is out of range
   */
  public void insertAttributeAt(int position) {

    if (m_Dataset != null) {
      throw new RuntimeException("Instance has accesss to a dataset!");
    }
    if ((position < 0) ||
	(position > numAttributes())) {
      throw new IllegalArgumentException("Can't insert attribute: index out "+
                                         "of range");
    }
    forceInsertAttributeAt(position);
  }

  /**
   * Tests if a specific value is "missing".
   *
   * @param attIndex the attribute's index
   */
  public boolean isMissing(int attIndex) {

    if (Double.isNaN(m_AttValues[attIndex])) {
      return true;
    }
    return false;
  }

  /**
   * Tests if a specific value is "missing". Does
   * the same thing as isMissing() if applied to an Instance.
   *
   * @param indexOfIndex the index of the attribute's index 
   */
  public boolean isMissingSparse(int indexOfIndex) {

    if (Double.isNaN(m_AttValues[indexOfIndex])) {
      return true;