weka.classifiers.rules.DecisionTableHashKey.java Source code

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Here is the source code for weka.classifiers.rules.DecisionTableHashKey.java

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/*
 *   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 3 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, see <http://www.gnu.org/licenses/>.
 */

/*
 *    DecisionTableHashKey.java
 *    Copyright (C) 2007-2012 University of Waikato, Hamilton, New Zealand
 *
 */
package weka.classifiers.rules;

import java.io.Serializable;

import weka.core.Instance;
import weka.core.Instances;
import weka.core.RevisionHandler;
import weka.core.RevisionUtils;

/**
 * Class providing hash table keys for DecisionTable
 */
public class DecisionTableHashKey implements Serializable, RevisionHandler {

    /** for serialization */
    static final long serialVersionUID = 5674163500154964602L;

    /** Array of attribute values for an instance */
    private double[] attributes;

    /** True for an index if the corresponding attribute value is missing. */
    private boolean[] missing;

    /** The key */
    private int key;

    /**
     * Constructor for a hashKey
     *
     * @param t an instance from which to generate a key
     * @param numAtts the number of attributes
     * @param ignoreClass if true treat the class as a normal attribute
     * @throws Exception if something goes wrong
     */
    public DecisionTableHashKey(Instance t, int numAtts, boolean ignoreClass) throws Exception {

        int i;
        int cindex = t.classIndex();

        key = -999;
        attributes = new double[numAtts];
        missing = new boolean[numAtts];
        for (i = 0; i < numAtts; i++) {
            if (i == cindex && !ignoreClass) {
                missing[i] = true;
            } else {
                if ((missing[i] = t.isMissing(i)) == false) {
                    attributes[i] = t.value(i);
                }
            }
        }
    }

    /**
     * Convert a hash entry to a string
     *
     * @param t the set of instances
     * @param maxColWidth width to make the fields
     * @return string representation of the hash entry
     */
    public String toString(Instances t, int maxColWidth) {

        int i;
        int cindex = t.classIndex();
        StringBuffer text = new StringBuffer();

        for (i = 0; i < attributes.length; i++) {
            if (i != cindex) {
                if (missing[i]) {
                    text.append("?");
                    for (int j = 0; j < maxColWidth; j++) {
                        text.append(" ");
                    }
                } else {
                    String ss = t.attribute(i).value((int) attributes[i]);
                    StringBuffer sb = new StringBuffer(ss);

                    for (int j = 0; j < (maxColWidth - ss.length() + 1); j++) {
                        sb.append(" ");
                    }
                    text.append(sb);
                }
            }
        }
        return text.toString();
    }

    /**
     * Constructor for a hashKey
     *
     * @param t an array of feature values
     */
    public DecisionTableHashKey(double[] t) {

        int i;
        int l = t.length;

        key = -999;
        attributes = new double[l];
        missing = new boolean[l];
        for (i = 0; i < l; i++) {
            if (t[i] == Double.MAX_VALUE) {
                missing[i] = true;
            } else {
                missing[i] = false;
                attributes[i] = t[i];
            }
        }
    }

    /**
     * Calculates a hash code
     *
     * @return the hash code as an integer
     */
    public int hashCode() {

        int hv = 0;

        if (key != -999)
            return key;
        for (int i = 0; i < attributes.length; i++) {
            if (missing[i]) {
                hv += (i * 13);
            } else {
                hv += (i * 5 * (attributes[i] + 1));
            }
        }
        if (key == -999) {
            key = hv;
        }
        return hv;
    }

    /**
     * Tests if two instances are equal
     *
     * @param b a key to compare with
     * @return true if both objects are equal
     */
    public boolean equals(Object b) {

        if ((b == null) || !(b.getClass().equals(this.getClass()))) {
            return false;
        }
        boolean ok = true;
        boolean l;
        if (b instanceof DecisionTableHashKey) {
            DecisionTableHashKey n = (DecisionTableHashKey) b;
            for (int i = 0; i < attributes.length; i++) {
                l = n.missing[i];
                if (missing[i] || l) {
                    if ((missing[i] && !l) || (!missing[i] && l)) {
                        ok = false;
                        break;
                    }
                } else {
                    if (attributes[i] != n.attributes[i]) {
                        ok = false;
                        break;
                    }
                }
            }
        } else {
            return false;
        }
        return ok;
    }

    /**
     * Prints the hash code
     */
    public void print_hash_code() {
        System.out.println("Hash val: " + hashCode());
    }

    /**
     * Returns the revision string.
     * 
     * @return      the revision
     */
    public String getRevision() {
        return RevisionUtils.extract("$Revision$");
    }
}