/*
* 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.
*/
/*
* BallNode.java
* Copyright (C) 2007 University of Waikato, Hamilton, New Zealand
*/
package weka.core.neighboursearch.balltrees;
import weka.core.DistanceFunction;
import weka.core.Instance;
import weka.core.DenseInstance;
import weka.core.Instances;
import weka.core.RevisionHandler;
import weka.core.RevisionUtils;
import java.io.Serializable;
/**
* Class representing a node of a BallTree.
*
* @author Ashraf M. Kibriya (amk14[at-the-rate]cs[dot]waikato[dot]ac[dot]nz)
* @version $Revision: 5987 $
*/
public class BallNode
implements Serializable, RevisionHandler {
/** for serialization. */
private static final long serialVersionUID = -8289151861759883510L;
/**
* The start index of the portion of the master index array,
* which stores the indices of the instances/points the node
* contains.
*/
public int m_Start;
/**
* The end index of the portion of the master index array,
* which stores indices of the instances/points the node
* contains.
*/
public int m_End;
/** The number of instances/points in the node. */
public int m_NumInstances;
/** The node number/id. */
public int m_NodeNumber;
/** The attribute that splits this node (not
* always used). */
public int m_SplitAttrib = -1;
/** The value of m_SpiltAttrib that splits this
* node (not always used).
*/
public double m_SplitVal = -1;
/** The left child of the node. */
public BallNode m_Left = null;
/** The right child of the node. */
public BallNode m_Right = null;
/**
* The pivot/centre of the ball.
*/
protected Instance m_Pivot;
/** The radius of this ball (hyper sphere). */
protected double m_Radius;
/**
* Constructor.
* @param nodeNumber The node's number/id.
*/
public BallNode(int nodeNumber) {
m_NodeNumber = nodeNumber;
}
/**
* Creates a new instance of BallNode.
* @param start The begining index of the portion of
* the master index array belonging to this node.
* @param end The end index of the portion of the
* master index array belonging to this node.
* @param nodeNumber The node's number/id.
*/
public BallNode(int start, int end, int nodeNumber) {
m_Start = start;
m_End = end;
m_NodeNumber = nodeNumber;
m_NumInstances = end - start + 1;
}
/**
* Creates a new instance of BallNode.
* @param start The begining index of the portion of
* the master index array belonging to this node.
* @param end The end index of the portion of the
* master index array belonging to this node.
* @param nodeNumber The node's number/id.
* @param pivot The pivot/centre of the node's ball.
* @param radius The radius of the node's ball.
*/
public BallNode(int start, int end, int nodeNumber, Instance pivot, double radius) {
m_Start = start;
m_End = end;
m_NodeNumber = nodeNumber;
m_Pivot = pivot;
m_Radius = radius;
m_NumInstances = end - start + 1;
}
/**
* Returns true if the node is a leaf node (if
* both its left and right child are null).
* @return true if the node is a leaf node.
*/
public boolean isALeaf() {
return (m_Left==null && m_Right==null);
}
/**
* Sets the the start and end index of the
* portion of the master index array that is
* assigned to this node.
* @param start The start index of the
* master index array.
* @param end The end index of the master
* indext array.
*/
public void setStartEndIndices(int start, int end) {
m_Start = start;
m_End = end;
m_NumInstances = end - start + 1;
}
/**
* Sets the pivot/centre of this nodes
* ball.
* @param pivot The centre/pivot.
*/
public void setPivot(Instance pivot) {
m_Pivot = pivot;
}
/**
* Returns the pivot/centre of the
* node's ball.
* @return The ball pivot/centre.
*/
public Instance getPivot() {
return m_Pivot;
}
/**
* Sets the radius of the node's
* ball.
* @param radius The radius of the nodes ball.
*/
public void setRadius(double radius) {
m_Radius = radius;
}
/**
* Returns the radius of the node's ball.
* @return Radius of node's ball.
*/
public double getRadius() {
return m_Radius;
}
/**
* Returns the number of instances in the
* hyper-spherical region of this node.
* @return The number of instances in the
* node.
*/
public int numInstances() {
return (m_End-m_Start+1);
}
/**
* Calculates the centroid pivot of a node. The node is given
* in the form of an indices array that contains the
* indices of the points inside the node.
* @param instList The indices array pointing to the
* instances in the node.
* @param insts The actual instances. The instList
* points to instances in this object.
* @return The calculated centre/pivot of the node.
*/
public static Instance calcCentroidPivot(int[] instList, Instances insts) {
double[] attrVals = new double[insts.numAttributes()];
Instance temp;
for(int i=0; i<instList.length; i++) {
temp = insts.instance(instList[i]);
for(int j=0; j<temp.numValues(); j++) {
attrVals[j] += temp.valueSparse(j);
}
}
for(int j=0, numInsts=instList.length; j<attrVals.length; j++) {
attrVals[j] /= numInsts;
}
temp = new DenseInstance(1.0, attrVals);
return temp;
}
/**
* Calculates the centroid pivot of a node. The node is given
* in the form of the portion of an indices array that
* contains the indices of the points inside the node.
* @param start The start index marking the start of
* the portion belonging to the node.
* @param end The end index marking the end of the
* portion in the indices array that belongs to the node.
* @param instList The indices array pointing to the
* instances in the node.
* @param insts The actual instances. The instList
* points to instances in this object.
* @return The calculated centre/pivot of the node.
*/
public static Instance calcCentroidPivot(int start, int end, int[] instList,
Instances insts) {
double[] attrVals = new double[insts.numAttributes()];
Instance temp;
for(int i=start; i<=end; i++) {
temp = insts.instance(instList[i]);
for(int j=0; j<temp.numValues(); j++) {
attrVals[j] += temp.valueSparse(j);
}
}
for(int j=0, numInsts=end-start+1; j<attrVals.length; j++) {
attrVals[j] /= numInsts;
}
temp = new DenseInstance(1.0, attrVals);
return temp;
}
/**
* Calculates the radius of node.
*
* @param instList The indices array containing the indices of the
* instances inside the node.
* @param insts The actual instances object. instList points to
* instances in this object.
* @param pivot The centre/pivot of the node.
* @param distanceFunction The distance fuction to use to calculate
* the radius.
* @return The radius of the node.
* @throws Exception If there is some problem in calculating the
* radius.
*/
public static double calcRadius(int[] instList, Instances insts,Instance pivot,
DistanceFunction distanceFunction)
throws Exception {
return calcRadius(0, instList.length-1, instList, insts,
pivot, distanceFunction);
}
/**
* Calculates the radius of a node.
*
* @param start The start index of the portion in indices array
* that belongs to the node.
* @param end The end index of the portion in indices array
* that belongs to the node.
* @param instList The indices array holding indices of
* instances.
* @param insts The actual instances. instList points to
* instances in this object.
* @param pivot The centre/pivot of the node.
* @param distanceFunction The distance function to use to
* calculate the radius.
* @return The radius of the node.
* @throws Exception If there is some problem calculating the
* radius.
*/
public static double calcRadius(int start, int end, int[] instList,
Instances insts, Instance pivot,
DistanceFunction distanceFunction)
throws Exception {
double radius = Double.NEGATIVE_INFINITY;
for(int i=start; i<=end; i++) {
double dist = distanceFunction.distance(pivot,
insts.instance(instList[i]), Double.POSITIVE_INFINITY);
if(dist>radius)
radius = dist;
}
return Math.sqrt(radius);
}
/**
* Calculates the centroid pivot of a node based on its
* two child nodes (if merging two nodes).
* @param child1 The first child of the node.
* @param child2 The second child of the node.
* @param insts The set of instances on which
* the tree is (or is to be) built.
* @return The centre/pivot of the node.
* @throws Exception If there is some problem calculating
* the pivot.
*/
public static Instance calcPivot(BallNode child1, BallNode child2,
Instances insts) throws Exception {
Instance p1 = child1.getPivot(), p2 = child2.getPivot();
double[] attrVals = new double[p1.numAttributes()];
for(int j=0; j<attrVals.length; j++) {
attrVals[j] += p1.value(j);
attrVals[j] += p2.value(j);
attrVals[j] /= 2D;
}
p1 = new DenseInstance(1.0, attrVals);
return p1;
}
/**
* Calculates the radius of a node based on its two
* child nodes (if merging two nodes).
* @param child1 The first child of the node.
* @param child2 The second child of the node.
* @param pivot The centre/pivot of the node.
* @param distanceFunction The distance function to
* use to calculate the radius
* @return The radius of the node.
* @throws Exception If there is some problem
* in calculating the radius.
*/
public static double calcRadius(BallNode child1, BallNode child2,
Instance pivot,
DistanceFunction distanceFunction)
throws Exception {
Instance p1 = child1.getPivot(), p2 = child2.getPivot();
double radius = child1.getRadius() + distanceFunction.distance(p1, p2) +
child2.getRadius();
return radius/2;
}
/**
* Returns the revision string.
*
* @return the revision
*/
public String getRevision() {
return RevisionUtils.extract("$Revision: 5987 $");
}
}